This is a drill recommended mostly for intermediate and advanced players. There can be one, two or any number of players participating. 
The purpose of this is to make the players aware of what it takes to hit the ball hard and still be able to make it land inside the lines. This is accomplished by imparting a large amount of spin on the ball.

Drill: Players grab 10 balls each and place them behind the baseline, on the same side. They keep a safe distance from each other so that none of them is hindered. 
Each player, one at a time, will pick a ball, let it bounce in front of them and hit it as hard as they can, still trying to make it bounce inside the lines on the opposite side of the net. 
Their goal is to hit the ball hard with a good amount of spin and make it bounce only once before it hits the back fence. The bounce has to be inside the court though. 
Players are awarded one point for a successful shot. 
If the ball bounces two or more times before it hits the back/side fence or the ball stops in the net, no points are awarded.
After they hit all 10 balls, the winner is the one with the most successful hits.