You don't have to drink that much to get dehydrated. Even if you don't even feel buzzed, you're gonna need to drink at least 2-3 glasses of water before you go to bed to make sure you're not dehydrated. Then you won't feel so bad on the bike the next day.

When I lived with 8 guys on the cycling team at UCSB, we used to party just about every night. Keggers, hard liquor, you name it. We'd have a 2nd fridge just to store our beer! But, we always made the 2pm club ride.