4 or More
Everyone sits around a table, then place a pint glass in the centre. The starting player puts some of their drink into the glass in the centre. That player can put in as much or as little as they want. If you are feeling lucky, fill it up!
That player then flips the coin and guesses heads or tails in the air. If the player gets it wrong they drink it. if the player gets it right, the coin gets passed to the player on their left and the game continues.
If everyone guesses correctly until the glass is full, the coin keeps getting flipped until someone gets it wrong. Then they must drink the contents. This person also gets to choose who starts the game again.