|Best with 5 or 6 players in a circle, though can be less or more.
The game starts with everyone putting a clenched fist into the circle. Whoever shotguns first starts (the loser will start after one game has been played). They hit each fist adding 5 on each time. This is only done once to show the maximum number that can be said and to set a rhythm to shout out to.
For 4 people, I would shout out 5, 10, 15, 20 (20 would be my own fist) followed by any one of these (the point is it has to be a multiple of 5). As I shout out the number each player can either extend their hand (5) or keep it clenched (0). If I manage to guess the total (10 would be 2 people with 5 and 2 with 0) then I am out of the game. If not play continues and the next person must shout out a number (must be 5, 10, 15 etc..) between 0 and the largest possible multiple of 5.
The last person remaining has to see off the whole beer. However, playing with diesel (half beer, half cider, blackcurrant) is a hell of a lot better. When your down to the final 2 people in a game it's a big adrenaline buzz. Once the game is over the game starts again with the loser being the starter.