Best idea or worst idea?
1.) Take a shot every time the Barbarian ruins something interesting or stealthy.
2.) Take two shots every time that sweet young thang turns out to be a succcubus who wants to eat your soul.
Drink once when you encounter a swarm in a Society scenario.
Drunken Master: Drink when you drink?
This probably goes without saying, but, take 2 shots whenever you roll a 1?
Drunken Master: Drink when you drink?
S%@& I'd be plastered by the second fight.
Whilst not a direct PF drinking game, there's always Drinking Quest marketed as "The world's first drinking RPG".
But if you want to regiment drinking at PF game night allow me to coin the term "Prole's Pathfinder Pourfest":
If you kill an enemy, you get to assign a drink to any party member (or maybe any party member that did not damage the enemy in that round, if you kill them before anyone else has had their turn, or after everyone else damaged them, you have to finish your current drink).
If you need healing you drink corresponding to the amount of heal you need
(CLW= 1D6, so drink a shot. CMW= 2 shots or a large swig, CSW= Finish your drink and pray to Caidean Caillean for healing, etc..)
Initiative is determined by who can finish their drink first (and yes, that means the DM get's to drink at least once per encounter) so everyone does a shot and last one with the glass empty on the table goes last.
Various bonuses on rolls depending on feats of drinking proficiency (+1 for a chug, team morale bonus for a waterfall effect, +4 on a roll for drinking an excessively large amount in a challenging manner, such as upside down, underwater, out of a fire extinguisher, etc....)
Ta da, one, maybe two encounters, and everyone will be rolling fort saves to stay conscious at the table. Oooh, fail a save and you have to drink, make a save and you get a "get out of jail free" card (maximum of 2 at a time) that you can use whenever you need to drink, or to "aid another". The unscrupulous types with a hearty constitution could take the opportunity to boost their coffers in exchange for a bit of relief.
Ability drain or other gradual conditions require a shot, negative levels result in having to chug from the King's Cup (everyone contributes a bit of whatever their drinking, leading to a lovely medley of beer+liquor+cocktail which is usually fairly disgusting).
If you don't get with-in 3 of the DC/AC/etc... on a check, you must drink a shot per each multiple of 3 you are off by (DC 20, you have an 11, congrats, you're drinking 3 shots!)
Depending on how integral you want drinking to be, maybe have some feats to reduce penalties, improve your opportunities to opt out, etc...
Hopefully some of these are usable, and of course be sure to drink responsibly and ensure someone has the Designated Driver archetype, maybe have a cleric on hand to handle any alcohol poisoning, as things could get messy quick.