Flow of pressure in water bottle Say you would have a plastic bottle partially containing water that is laying on its side. How would applying external pressure through a weight on the side affect the internal pressure. In other words, how well does the pressure transfer from outside to inside the system? 
 A: Based on your comments I'd say you're on the right path on your own.
You already mentioned using the (ideal) gas laws.  Beyond that there isn't a whole lot to consider in this problem.  (assuming you want to do a cursory analysis of this situation, and not find exact pressure values or anything like that)
It's worth noting that water is approximately incompressible, so it doesn't build pressure quite like the gas does, but as long as the gas is pressurized the water will be at that pressure (and a bit higher the deeper you go, see hydrostatic pressure).
So the basic concept is apply a weight > deform the container > reduced air volume means increased pressure in the bottle due to ideal gas law.
Your rewording of the question is a bit more complicated.  The effectiveness of transferring pressure between outside and inside depends quite a bit on the material of the bottle.  Depending on the material, it will deform more or less when you apply a force to it.  
A weak material, like a balloon very easily deforms, so it's very easy to apply a force to the outside and increase the pressure inside.  Something like a steel container doesn't work as well.  When you apply a force it does deform a bit, which would increase the pressure; but it barely deforms, so the volume barely changes and pressure barely increases.
A: Pressure is $\frac{F}{m^2}$. If we apply a force $W$ on one side, we must apply an equal and opposite force on the other side of the bottle. Therefore, the increase in pressure in the bottle when the weight is applied is $\frac{2W}{\text{Surface Area Of Bottle}}$. If you increase the surface area of the bottle, the increase in pressure will be lower.
A: It's not so simple. For example, try to open such a bottle and place something light (e.g. coin) on it. Obviously you will have no pressure transfer at all (pressure inside and outside will be the same), but the bottle will not collapse.
