It was a first for us. Alex earned enough rewards that he had to pick and choose among them.
He earned sufficient bus tokens for a bus ride. (He earns tokens by having a dry bed and by cooperating with brushing his hair.)
He also earned an ice-cream and Xbox time. (By having a BM in the toilet.)
I gave him the choice of which reward would take priority. We can't both ride the bus and play on the Xbox, so he could choose to have the Xbox and do the bus ride later or he could choose to do the bus ride today. (I considered offering him the option of Xbox the following morning but decided against it since we usually have a bit of a behaviour burst after a success.)
Alex's decision was to have the bus ride, then the ice cream, and then, if there was time, some Xbox. It turned out that we got home from the bus close to 7, which meant he had to further choose. He could get the ice cream through the drivethru and still have time for Xbox or he could eat the ice cream at McDonald's. He usually prefers to eat at McDonald's, so I wasn't surprised when that was what he picked.
I was pleased by how he took time to think about what he wanted before making a choice, rather than just blurting something out. I think he's starting to understand that he does have control over some aspects of his life.