If you're short players only have one at second base and shortstop. Start with a runner on first. Have catcher call the bunt defense as he would in a game. Hitter bunts the ball and the defense executes the play. Leave runner on first and second.
Catchers calls defense for the situation.
Hitter bunts the ball and the defense executes the play. This should be a quick paced drill that places pressure on the player's to perform. You can add squeeze bunt defense into the drill also. This is a chance to see how your players react to a pressure situation. If a pitcher throws a couple balls, make him get to the end of the line.