Sorry

Drink once when someone sends you to start, twice when it's a 'sorry'.
Players drink when someone leaves start (except that player).
When switching positions with another player they must drink.
Everyone drinks when a player gets home.
Drink twice when you get a 4 (go backwards), if the 4 brings you close to home (i.e. you get it after leaving start) everyone else drinks.
If a player lands on your 'slide' drink, drink twice if they slide.
Loser finishes drink.