Question

what happens to the force if some water is added in the bottle ?​

Answer 1

If you drop a bottle without any residual motion (that is, it is not spinning etc) then everything inside that bottle will be in "free fall". The air and the water will attempt to fall at the same rate.
There is a nice video of what happens to water when it "spills" in the International Space Station: it becomes a "blob" because of the surface tension. Add to that a small amount of attraction between the liquid and the bottle it is in (hydrophilic surface - attracting rather than repelling water) and you see that the water will actively want to stay in the bottom of the bottle: there is no force to move it away, and there is actually a (weak) force keeping it there.
So the air stays on top, and the water at the bottom. When it hits the ground, it will make a big mess - but that's not what you were asking about...