When you go out to eat does the condensation from your glass cause the napkin to stick to the bottom of it? Here is a neat tip to keep that from happening!
Sprinkle a little salt on the napkin!
Why does it work?
Water has a high surface tension. It's like when you fill up a glass, you can fill it slightly higher than the rim - it sort of bubbles over. It's also what causes bubbles to form (whereas more viscous liquids like oil tend to flow more smoothly).
Surface tension in water is due to the fact that water is a dipole. The electrons are slightly off-balance in each molecule, causing the water to "stick together" by arranging itself in a magnetically attractive fashion. This is also why water crystallizes.
The "sticking together" is what causes the napkin, coaster, or whatever to stick to the glass or bottle.
Salt is an ionic compound. When dissolved, it introduces positive and negative ions into the water. This essentially dissipates much the surface tension. That stops it from sticking as easily. There you have it.