Alcohol is a very strong diuretic. Maybe "There isn't really anything that dehydrates you" wasn't the best way to phrase it. I wanted to state that a diuretic only causes dehydration if you don't replace what has passed through. So you cause water to pass through more quickly, but you can also replace it at a faster rate and not dehydrate. After a lot of drinking I have between 1 and 2 quarts of water. That usually does the trick. No Jim Beam though. I'm more of scotch kind of guy. hehe :)
Water molecules are used when the liver metabolizes the ethanol molecule:
So even if you don't pee or sweat out any water, one can still become dehydrated by drinking alcohol.