Short-long (attack defence position 1 & 5) in 3 teams
See picture. Each 3 (or 4) players 2 balls. 2 players at the net a few meters apart, other player(s) in the backfield.
Exercise 1: Players take turns throwing the ball, player in the backfield plays the ball back underarm.
Exercise 2: First ball comes deep, 2nd ball comes short
Exercise 3: Throwers stand a little further apart and throw straight: player with ball on the sideline throws deep, other short. Passer moves left/right.
After x-number of balls or after some time swap places.