In a follow up to using canteen caps as spoons I present food preparation with canteens. 

Food preparation could involve canteens as found in:

Stedman, Charles. "The History of the Origin, Progress, and Termination of the American War, Vol 2." London. 1794.

"For five days it was supported upon Indian corn, which was collected as it stood in the field, five ears of which were the allowance for two soldiers for twenty-four hours. They were to cook it as they could, which was generally done by parching it before the fire. In riding through the encampment of the militia, the Author discovered them grating their corn which was done by two men of a mess breaking up their tin canteens, and with a bayonet punching holes through the tin; this made a kind of a rasp, I which they grated their corn: The idea was communicated to the adjutant-general, and it was afterward adopted throughout the army."

or in An Original And Authentic Journal Of Occurrences During The Late American War: From Its Commencement To The Year 1783 by Sergeant Roger Lamb Royal Welch Fusiliers

"Sometimes we had turnips served out for our food, when we came to a turnip field; or arriving at a field of corn, we converted our canteens into rasps and ground our Indian corn for bread;.”

A rasp might have looked like this.

And it was done in the Civil War.

Here is a canteen from the Museum of the Confederacy.

Si Klegg wrote: In the fall, when the corn in the fields was hardening, he took a half-canteen, stabbed it full of holes with his bayonet, from the inside, and the convex surface made an excellent grater, and a dish of "samp"

Canteens could have been used in the cooking process. Feature 2 in the excavation of a fireplace in a hut at Crown Point yielded a flattened canteen that may have served as broilers or fryers. There was also a flattened lantern panel.

Placing the canteen over the hole in the fire pit may have served as a cooking surface

Fisher , Charles L . (1995) "The Archaeology of Provincial Officers' Huts at Crown Point State Historic Site ,"Northeast Historical Archaeology:Vol. 24

Si Klegg wrote "The old canteen was thrown into the fire and the heat soon melted the solder by which the halves were joined, and the soldier found himself in possession of two tin basins eight or ten inches across and in the center about two inches deep."

And all the Progressive Civil war reenactors have a canteen half to use as a skillet.