This is a great issue. It could easily be it's own forum topic. But which forum, operations or employment?????
I've worked with a guy that actually taken a small cock pot on long pool trips. He is famous for chili dogs. Since the cock pot is just a heating source, it is not effected by the 75 VDC current. I've also worked with guys that take cup size heaters for hot soup. (Just don't run them dry.) Again, not effected by 75VDC.
I've made roast beef with cheddar cheese, wrapped them in foil and reheated them either on the side wall heater or if summer, in the engine compartment on the engineers side of a -9. (There's a small access door [about 9 inches high by 18 long] just before the air compressor compartment that stays nice and warm.) Leave it there for about an hour, and you're ready to eat. Basically anything that can be sealed up can be heated in the engine compartment. In certain parts of the engine compartment, Tupperware will survive nicely. Just make sure that it is the hot air in the compartment that is warming the food and not the heat from the surface it is sitting on.
You can drain water bottles for cold milk if you have a cooler to keep it cold. Put cereal in tupperware and you're ready for some breakfast.
Progresso soup is good too, just make sure you pop the lid open to prevent from being burned when it explodes. BNSF recently had an accident where that happened.
One problem I've always had was the bread getting mushy when put into a plastic bad then into an ice chest. I tried putting cardboard down between the bottom of the basket that fits on the top part of the chest, but no luck. The bottom just gets too cold and the bread gets wet. Any ideas on how to keep the bread dry while keep the meat and other items cold?