I have two kids on the spectrum. My oldest has social anxiety. Just recently he had a performance in front of a large audience. The night before he had a huge amount of nervous energy. This ball fidget toy helped work off that energy. There's some exercises ,on the box ,to keep the user busy. The ball fidget toy also lights up. So it can be made into a game with other users.
To me it was relaxing to loop the string around my finger and roll the toy between my palms. That's a good way to be kind of secretive about using the toy.