You must have at least 3 people to play. Get as many shot glasses and beers as you have players. You begin with one beer, the first person fills up his/her shot glass and takes a shot. Then passes the beer to the next player. They take a shot then pass the beer to the next and so on and so on.
Continue doing this until you have finished all of the beers you are playing with. The beer will not hit you all at once, but once it does beware.