Here’s a favorite conditioning/defensive footwork drill.  It’s called 1000 MPH. “  Needless to say,it’s fast paced and gets a lot of players involved.

1000 MPH Drill
Line players up at each lane line, but behind the baseline and have the 2 lines face the opposite baseline.

On the coach’s first whistle the first 2 players break out to the elbow, turn, breakdown into a defensive stance and foot-fire.

On the next whistle they swing step towards the half-court/sideline intersection to simulate a trap (players swing, 2 slides, run, and finish with 2 slides to trap).

Next whistle they swing, 2 slides, run and 2 slides to finish at the elbows at the other end of the court.

Next whistle swing, 2 slides, run, 2 slides to trap in baseline/sideline corner.

Next whistle sprint back to start and swap lines

Once the players know the drill, have 2 players go on each whistle, so you can have 8 involved at the same time.