This was one of my favorites. Not in the C-Ration Cookbook from Tabasco, think it was published in Stars and Stripes, but I had it whenever I could get the ingredients.
One can: Beef, spiced, with sauce
One can: cheese (preferably cheddar)
One can: white bread
One cracker
Remove bread from the can, cut into three slices. Place one slice of bread in a can, cover it with meat and cheese, top with another slice of bread, cover it with meat and cheese, top with a third slice of bread, and cover it with the remaining meat and cheese. Using the cracker, smash the whole mess down into the can. Place it in an empty C-ration box and set fire to the box. When the ashes cool, enjoy.