I found this wonderful site called It's Always Autumn along with this terrific recipe. Please check out the blog post for a step-by-step tutorial. The blogger says all you need to make any flavor of baked, not fried, doughnuts are one dry cake mix, one egg, 1/4 cup of vegetable oil, and a cup of water.
She includes a recipe for glaze and says that even making 10 dozen mini doughnuts using five different flavors of cake mix took her less than two hours. Sounds like a good bake sale product to me!