[itworkslikethat]

You can. It takes some drugs, but you can. It's not uncommon for people to die because of dehydration at parties (taking stuff like extasis, etc). Regular users of methamphetamines also have this problem - they just don't realize they're completely dehydrated.

My point is that this comparison doesn't make sense. A cloud rains because it's undergoing a physical process. You drink because you decided to drink (and only then, inside your body, the water is undergoing a physical process). It's usually hard to decide not to drink, but still - there's a huge categorical difference in what's happening in either case.