Originally Posted by
bdschobel
It contains lots of gas molecules at a minimum, some of which no doubt are water vapor. Drinking from your bottle can't totally empty it -- and doesn't even come very close, really.
"It's not empty... it contains 20% of a highly flammable gas in a carrier matrix of inert nitrogen and argon gas. Oh and of course there are probably some impurities like dihydrogen monoxide and dioxidocarbon."
Please please please someone say this next time they try to take an empty bottle.