Each member of the team has a USB 'sweet dispenser' connected to their computer (this would need to be invented, but sounds like a brilliant Arduino project).
When you feel another team mate has done something good or worthy, you can hit a button which gives them a sweet!
...but of course, you can not give yourself a sweet!
Genius!
How about sweet you say "Way to go Bro!"? and why use an arduino at all? Waste of resources just stick with a small lightweight digital program to 'send' a sweet (or Way to go Bro!) to them directly.
The software program was a semi-serious suggestion.