What are the exercises I can do for my sprain ankle?

Stretch easily. If your ankle is steadily improving, you may begin stretching exercises, but passive range of motion (no weight or force of gravity or muscle) the best stretches for leg and ankle-using stretching bands or towel, sitting with leg extended and place the band under the foot like a stirrup, and gently pull your foot to the inside and the to the outside. There should be minimal pain.
Depends on diagnosis. Some may be helpful while others my cause you harm depending on your condition. Discuss it with you physician or your physical therapist.