Simple cat toy to print out. Use PLA filiment for best results. You can fill the ball with catnip or treats to entice your cat cat to play with it. The more it plays with it, the more likely a treat is to fall out.
Sadly.... my dumb cats aren't interested! But I wonder if you watch the print, would it be possible to put a metal ball inside or a small "bell" type ball? Some cats like that. So, for anyone reading this, try pausing the print and dropping something that make noise? This print works great, the ball rolls nicely. Your cat may be smarter than mine.