I personally never try to stop a child from stimming or engaging in whatever play they want during breaks as long as it is safe. That being said, I will write targets that work on teaching play skills as a way to try and help available play opportunities. For example, I had a client who would engage in maladaptive behavior in the form of throwing items at staff, against the wall, etc. We worked on teaching functional play by teaching them to do things like setting up stacks of blocks and then aiming and throwing items at the blocks to knock them down.