Clear all the original chess pieces off of the board and replace them with shot glasses. Use different shot glasses for each chess piece. Fill each shot glass before the game starts.
Play the game as the normal as the instructions describes. Every time a chess piece is lost you must take the shot before it leaves the board.
King and queen pieces should be stronger spirits. The looser of the game must also drink their entire drink.
If you do not have that many shot glasses, just take a shot for every Chess piece of yours that leaves the board.