There are two teams, lined up single file behind the baseline, opposite sides. The coach is at the net post, having a basket of balls ready to feed from.
Drill:
The first two players from each line will take up positions at the baseline, one on the deuce and one on the ad side (see graphic below).
The coach feeds the ball for the two teams to start the point/rally.
The two teams play the point while having every player that hits the ball move out to the end of the line and be replaced by the next player from his team.
Play like this until one of the teams wins 11 points.
This is a fun drill which limits the waiting in line especially for large groups of players.