This defensive basketball drill is going to help the player work on their defensive slide technique, conditioning, and lateral quickness. The cones are going to help remind the player to stay low as they defensive slide, and also give them a challenge to beat every time that they do the drill. If you do this drill during practice or basketball training you can also turn it into a competition between the players. You can set a penalty for the loser of the drill, this will really help to make sure that the players are giving all that they have.
Make sure though that the players are not sacrificing technique as they begin to compete and speed up, you don't want to develop any bad habits. Playing defense is often looked at as a chore by most basketball players, but hopefully this drill will help to get rid of some of that negativity, and get more players excited about playing defense.