Another drill that I use often as a means to emphasize and inculcate defending on the ball is the “paint game”. This is a drill that the players love because of the competitive elements.
SET UP: Split the players up into two teams. One team is on offense, and the other is on defense.
STEP 1: The offensive teams stays on offense for one minute straight. The only way that they can score is by driving the ball into the paint, landing in a jump stop, and maintaining possession until they pass the ball back out. A paint touch above the volleyball end line is 1, while a paint touch below the volleyball end line is 2.
STEP 2: After one-minute passes, total up the number of points the offense got. The offense and defense now switch and the new offense tries to beat the score while the new defense works to protect the paint and their lead.
A diagram of the drill can be seen below:
Also, here is a video of my team using this drill in practice: