Crane games make good money, and people are always willing to spend up to $5 trying to win a $1 prize. We have 4 crane games at Dave & Busters and they're consistently in our Top 10 list for sales. Our watch crane machine has a bunch of non-operational display watches on a rear shelf at eye-level inside the machine. At least once a week, a customer will ask me how to get the claw to grab them.

I usually look them right in the eye and tell them that all you need to do is press up up down down left right left right and start. People actually believe me until it doesn't work

You could stock it with cheap jewelry/trinkets or plush.
You could also just put in a candy/prize/sticker vending machine like the ones made by the Beaver Co.