Aren't they self heating? I thought you could hit the pack on something hard and the hot food will automatically heat up.
From
http://www.dscp.dla.mil/subs/rations/meals/mres.htm HOW DO I EAT IT?
Except for the beverages, the entire meal is ready to eat. While the entree may be eaten cold when operationally necessary, it can also be heated in a variety of ways, including submersion in hot water while still sealed in its individual entree package. Since mid 1992, a flameless ration heating device has also been packed into each meal bag to heat the entree.