How to pour water from a bottle as fast as possible? When one pours water out of a bottle, it first flows smoothly but then a pressure 'blockage' develops and the pouring becomes interrupted and turbulent, so that the water comes out in splashes. This seems to slow down the flow of water from the bottle.
What is the optimal way to pour the water so that it completely empties fastest?
Possible strategies:


*

*Holding the bottle at a certain angle

*Wildly shaking the bottle

*Squeezing the bottle

*Other...


It probably depends on the shape of the opening and/or the bottle itself, but we shall assume this beautiful example of a standard water bottle:

CLARIFICATION
The question is asking how to pour the water the fastest, so no straws, hole insertion and evaporating lasers allowed...
 A: Crush the bottle fast, beginning from the bottom. The same will be true for any elastic type bottle. 
It is only glass bottles that have an unsqueezable limit. I have found that if one shakes the glass bottle , the flow is faster and the bottle empties faster . Just did the experiment in the bathroom. Empties about twice as fast when shaken: slow up, fast down.
A: Option 3: Squeezing the bottle. Of course it depends how much pressure you are able to do, the strongest you are the fastest, and if you compress the bottle in an industrial press, the water will leave in a split second without breaking the bottle (well, it gets deformed, but that was an option).   
A: What I have observed is that if we turn the filled bottle (open) upside down and plug in a straw then the water starts to flow out faster. This happens because by plugging in a straw we make a way for air to come inside the bottle and fill empty space. Another observation that I've made is that when water is flowing out of a bottle (upside down) just shake it vertically. Inertia will act upon it. Make sure that while shaking you pull up the bottle with more force and you bring it down. If you do both with the same amount of force then inertia will act both ways and the time taken to flow will remain the same as in the ordinary case.
A: You spin the bottle so that the water comes out like a tornado. This lets the air come in faster through a tube of space in the middle. The air pushes up forcing the water out leaving a space in the middle for air to come in. The rate of water flow is exponential. This is because the water lessens letting air come in faster, pushing the water out faster with lessens the water level even more and it goes on and on
A: I am telling this from my practical experience. In my home we have very poor water supply so we purchase 15 ltr water dispenser for drinking water. The guy needs to take the bottle back. So he shakes the bottle such that water make a kind of whirlpool while still keeping it straight and then quickly turns it upside down at an angle. The water flows quickly out of bottle. I saw it working. However I must tell that design of the 15 ltr water dispenser is entirely different than 1 or 2 ltr water bottle. Also, if the water is filled till the neck one can not swirl it.
A: Hold the bottle upside down, your hand grasping it near the base.  Extend your arm downwards.  Make a circular, conical-shaped motion with your hand.  Keep it up until you have a nice vortex going.  Spinning too fast is counter productive; centrifugal force keeps too much water hugging the sides.  You need a speed just a bit more than what's necessary to create the vortex.   Stop the circular motion until the vortex disappears, at which point give it a little circular nudge to get the vortex going again.  
People who say the vortex method is not practical have not tried it.  I can't guarantee it's the fastest (how does one establish that?), but it's fast, and I put my money on this method.
A: I can only give you a hand-waving explanation, but the fastest way to empty a bottle I have empirically found is to pour it upside down but rotate the bottle. The main problem is that the empty space above the water needs to be filled again with air which can not get through. If you rotate the bottle correctly, an air corridor inside the bottleneck opens and air can constantly flow back into the bottle, thus creating a nice constant stream of water around the side of the bottleneck and no "spluttering" behaviour.
Edit:
To reflect and preserve a few useful additions that were made in the comment section:
Peter Diehr remarked that above only holds true for glass bottles. Squeezable plastic bottles can be emptied more quickly by compressing them and thus avoiding the empty volume that otherwise needs to be filled with air.
Stormwind apparently did a bit of real life experimenting which seems to support my answer as far as incompressible bottles without inserted straws or similar separate air inflows:

Upside down = 21 s, optimising air flow but bottle almost horizontal = 24 s, rotating bottle as in this answer = 14 s. 

A: Cut the bottle base and squeeze the bottle
The air pressure has a major role to play in this situation. If you keep the bottle vertical, there wouldn't be any room for the air to move in as the water falls through which is the reason why you see turbulence and interruptions.
There are various ways to tackle the issue. The best method would be to punch a hole at the base of the bottom and then pour in but that is just ridiculous. 
The other way round would be to share the mouth of the bottle. 
Arguments against the rotating the bottle idea
Of course, as Sanya said you could rotate the bottle to create a tube which passes through the water but I see complications.


*

*If the water is filled to the brim then you are going to have trouble getting a tube of air open through the middle (it's just difficult if you have a . 

*It is simply not practical to rotate a bottle. If you were to try to rotate while pouring it upside down, you can't do it that fast and there is a high chance that you are going get the mouths of the two bottles out of alignment and spill some of the water.

*Thirdly, it is impossible since you cannot make a whirlpool against the force of gravity. Even if you did holding it vertically and then suddenly turning it over, you won't have it for any longer than few seconds.
Arguments against the straw idea
Keeping a straw coming out of the mouth of the bottle isn't a practical one too (Shuvam's answer). 


*

*You can't keep perfect mouth to mouth contact between the bottles because the straw is going to come in the way. If you try to get too close, the straw is going to bend and serve no purpose.

*The straw is going to fall down (gravity + viscosity of water; water is flowing down, it will try to drag the straw along with it) so you would need one hand to hold onto the straw and another one on the bottle. 

*This is way too hard to initiate it. Let's say you place the straw when the bottle is vertical. Now, how are you going to turn it upside down? You won't be able to do it without spilling some of the water.
My impractical solution
In case the OP was accepting such impractical solutions, then my solution as said earlier would be to puncture a hole into the base of the bottle so that air can flow from the top for the bottle which is filled with water. On the bottle which is below, I would make two holes in opposite directions near the top so that air can escape from the bottle which is being filled without disrupting the flow.
That can be upgraded too. Cut the base and add a piston (could be any household utensil - maybe a glass stand?) and push the water down. There is no need for air to enter since the piston is pushing the water down.
If needed add some waterproof tape around the mouths of the two bottles to keep them in place? Just kidding.
My practical solution
My practical solution would be to pour the water into the bottle by keeping it at an angle. Initially being almost horizontal and slowly increase the inclination. In this solution, there is always a gap in the mouth of 'both' the bottles for the influx and outflux of air (influx for the bottle pouring the water, outflux for the bottle receiving the water. Moreover, you can transfer almost all of the water without spilling any. Another advantage of this idea is that you can correct the inclination as the water keeps flowing to give the maximum efficiency. You can see the rate at which the water is being filled with your own eyes and hence can alter the angle.
A: The question is: what is the optimal way to pour the water so that it [the bottle] completely empties fastest? I conclude the aim is to have the empty bottle, not the water in another container.
Solution: Create a centrifuge-like setup, bottle opening to the outside. The setup will generate artificial gravity for the water in non-inertial frame of reference associated with the bottle.
You may hold the bottle in your hand, stretch the arm and spin fast enough. Example videos below. There is no bottle in any video, so it looks like you have the chance to be the pioneer.


*

*Basic setup here.

*Use two bottles in two hands to create symmetric setup for balance. Unbalanced centrifugal setup may fail like this one.

*More technically advanced setup is possible: link.

*The setup is prone to miniaturization (notice the renewable energy source): link.


This solution may be combined with squeezing the bottle.
Enhancement: do it in vacuum (but watch the temperature and don't let the water freeze before it leaves the bottle). It is obvious and marvelously impractical thing to do. You may be picky again and expand your clarification now. :)
A: I assume you are not worried about the few drops that are always left in the bottle after pouring out the water. The reason I make this assumption is that without "evaporating lasers" being allowed every method suggested would need to wait hours for the drops to naturally evaporate. Even then, there would still technically be a tiny bit of water vapor in the air in the "empty" bottle.
Given this assumption I will propose the fastest way to empty 99% of the water in the bottle. With modern technology the fastest way to empty the bottle would be mounting it inside a metal projectile that will be launched from a rail gun. Point the opening of the bottle to the back of the rail gun and fire the projectile. According to https://en.wikipedia.org/wiki/Railgun the "General Atomics Blitzer system" (a railgun) can exert over 60,000 g force. With this kind of force the vacuum created behind the water as it comes out of the bottle will be negligible. Given say a 20 cm tall bottle and 60,000 g force. We know for constant acceleration that d=a*t^2/2. Therefore the water at the bottom of the bottle will take roughly 0.000368 seconds to travel the 20cm to the tip of the bottle. Of course this is to be taken as more of an "order of magnitude" calculation with the exact value determined with experimentation :)
A: A few years after asking this question I stumbled upon this super interesting video tweet, which is relevant for this question: link to tweet video.
The video shows two ways of emptying a certain water bottle. In one case, the bottle is simply flipped upside down. In the other case, the bottle is also flipped upside down and quickly moved in a circular pattern. The latter causes a kind of tornado current in the liquid, speeding up the emptying from 24s to 17s.
The video backs up the accepted answer. It is also rather interesting that the rotation does not have to be continued until the bottle is empty, but it is enough to start off the tornado current by a few rotations.
A: 1st- 
  Take any beverage of choice that comes in a aluminum can/soda can flip lip profile. Aluminum is easy to bend and has a good elasticity and will not fracture and hold its shape when modified, this experiment will work with any material if it can hold shape after modification. Thin Plastic might not hold structure and other material might fracture or be complicated to mold, so aluminum is the best container to use. 
2nd- 
  Open the can.
3rd- 
  The opening where you drink from is on the top of the can, On the side of the can right below the opening to drink from create a concave indentation with your thumb in the can about a 1/2" in depth.
4th- 
  If the steps to modify the can where done correctly One should notice a stronger constant flow of liquid momentum exiting the can without any pressure disruption.
A: *

*Put an straw thru the open cap of the bottle.

*Bend the straw so that you can blow into it while it is upside down.

*Turn the bottle upside down and blow as hard as you can.

A: go into a vacuum chamber
open the bottle
turn it upside down
gravity will do it in a second or two.
A: The fastest way to get that liquid out of a bottle is to insert a lot of air in while the liquid comes out. How you insert a lot of air only depends on your imagination.
