Things to entertain your beta fish?

You can use external stimulus. Things like changing the decor around his tank or placing colorful, shiny, or oddly shaped items around the tank. If you find a particularly interesting object for them, it can pique their interest for hours even. It might surprise you too what interests them. I have a small Eeyore plush with green cape that interested my older male so much he wouldn't even care when I walked in the room which was highly unlike him as he would always beg for food. I currently have a similar setup with live plants that ramshorns hitchhiked on. My current betta is occupied enough hunting them down. If you don't have a fixed aquarium setup that cannot be moved (like a planted tank), you can move the decor inside his tank around too. Ping pong balls floating on the top are particularly excellent I've discovered for betta that enjoy jumping. Floating objects in general (floating plants, floating betta logs to name a few) are good. Sometimes they respond to sound too. At least, I know they're behavior alters when I play music or my violin... XD whether or not that's a good or bad review of my playing is debatable.