For the record, I am very hungover right now, and I was just pondering to myself how I definitely was suffering penalties for the condition. (author's note: I wrote this first sentence and then literally just did nothing for an hour). My gift to you today is something we all need; more rules bloat! Yaaaaaay!

Hangover Rules
A character can drink several drinks before the dreaded hangover kicks in, but the exact amount varies from person to person and the situation. Typically, a character can drink up to twice their constitution modifier (minimum 2) in drinks before having to worry about ever having a hangover. After that, each drink consumed forces a Constitution check (DC=10+amount of drinks consumed). Any bonuses to saves against poisons may be added to this check, and immunity to poison ensures one never gets a hangover (and, indeed, can never get drunk!). The amount of times this check is failed determines how the character will feel in the morning.

• 1-2 failed saves: The thirsty condition. A thirsty character takes a -2 penalty on skill and ability checks. This condition lasts until the character drinks one good glass of water, or until they have been awake for at least an hour.
• 2-4 failed saves: The hungover condition. A hungover character takes a -2 penalty on all skill and ability checks, a -4 penalty on Perception checks, can neither run nor charge and takes a –2 penalty to Strength and Dexterity. This condition lasts 1d3 hours after the character drinks two good glasses of water, or until they have been awake for at least 1d6+1 hours.
• 5+ failed saves: The urrgh-what-the-hell condition. A urrgh-what-the-hell character takes a -4 penalty to all skill and ability checks, a -8 penalty on perception and concentration checks, and is considered nauseated and exhausted. This condition lasts for 2d6 hours, but if a the afflicted character consumes a gallon of water it is reduced to the hungover condition.