I used token reward in some of my sports psychology education classes with junior athletes. Since they were mostly under 12 years, I wanted the class to be fun and interactive. So I used the most simple reward form, where athletes who answered my questions got a present.
There were also instances where I conducted group activities with older athletes and they had to compete against themselves. The winning group got some rewards.
From these experience, I found that token reward was effective with junior athletes but not so much with the older ones. Older athletes preferred appreciative comments and criticism compared to tangible rewards.
I think I will practice token reward in future if I feel the class is getting bored, but not as frequent because I want the athletes to attend the class or do the activities because they want to, and not because of external reward.