In fact, the best thing to do is drink a tall glass of water before you go to sleep. Your body is taking all the fluid it can spare to wash out the toxins you filled your body up with. If you've ever been severely dehydrated before (I have), you'll notice that it feels quite a bit like a hangover.
And holding your pee does nothing to help stop dehydration. Once the fluid is in your bladder, it can not be reclaimed by the body.
Drinking water after getting drunk is NEVER bad. It may be distasteful to you psychologically, or it may bother you if your stomach is upset, but it's GOOD for you physically. Your intense headache and general malaise associated with a hangover is caused primarily by dehydration.
I'm 34, and did a stint in the army. My hard drinking days are behind me, but I had ten plus years of hard partying to figure this stuff out. Trust me, drinking a big glass of water or two before bed eases your hangover the next day. If it bothers your stomach, take a couple of tums with it.
You may not think you'll remember, but a couple of bad hangovers teach you a lesson no amount of alcohol can make you forget.
And just wait, guys, hangovers get worse the older you get. When I was in my late teens and early twenties, I could drink all night, and jump up outta bed to go to work or in the field (when I was in the army) the next morning with little more than a nagging headache. If I try drinking all night now, it puts me in bed for most of the following day.
Heh, one long night in Las Vegas this past August reminded me of this. I had free beers from 10PM until 5AM while I was going from casino to casino. I must have had about 18 to 20 beers that night. Needless to say, the next day was a total waste. Fifteen years ago, I'd would have been able to jump up uot of bed after four or five hours sleep, and function.
What a drag it is getting old...