This is a very common game with kids, but i think that adults enjoy it too. It's very funny when you see people going for the doughnuts.
Tie a rope between two poles. This rope has to be higher than the height of the participants. Then tie strings from the rope, some longer and some shorter. Have players start on the count of three. And then, with hands behind their back, they have to finish one doughnut. The first to finish wins.