Racquet sports brand Yonex has a big shop in Moho mall with a bunch of those single-player courts with ball machines. You can book a space on Dianping or the WeChat Mini Program, 棒棒体育, borrow a racquet for free, and try to hit the balls that the machine spits at you. The speed, angle, and spin are all adjustable with a remote. Prices are generally around 100-140rmb for the hour (when you book online; more expensive if you just roll up), and they also offer classes for adults, groups, and kids. Unlike some of these courts around town, there's no music here, but the view outside the big windows is nice. Nice workout for an hour, especially on a rainy day. This being Yonex, they have plenty of racquets, apparel, and other gear for sale too.