One of the most simple training drills in badminton is the multi feed shuttle drill where the coach holds a bunch o shuttles in one arm he uses the other arm to throw the shuttle.
The coach can vary the speed at which he is throwing the shuttle. Not only that, he can also vary the direction of the shuttle to be thrown depending on the level of his student.
We can add variation to this drill by making the coach to hold the racket one hand. With this, we can push the student a little further off the court rather than just in front of the court.