When I used to go camping with the Girl Scouts, we all had to bring tuna (yes, tuna!) cans or we couldn't have dessert.
My favorite - Pineapple Upside Down Cake
Make any boxed yellow cake mix according to directions.
In each tuna can put some melted butter, brown sugar, a pineapple ring and a cherry in the middle. Cover with cake mix (about 3/4 of the way to the top.) Cover with foil and lay in the coals until done -- sorry no time to give you, you must just keep checking, as it depends on the heat of the campfire.
Another - Gingerbread
Make a gingerbread mix according to directions. Put some applesauce in the tuna can, pour cake mix over it, cover with foil and place in coals to cook.