It isn't always the food per se, but the lack of hygiene there that gets 'em - as in fingers in all the food that are not properly sanitized.
Groan.... ugh
I usually choose really remote units to support, so I've fed a lot of Joe's who can't cook. In my experience, the tuna pouches are a good idea for the ease of use and the protein. If you can get some hot sauce, mayo or tarter sauce packets from a local fast food place to include, they'll really appreciate that with them. Also, they'll eat ready made canned foods heated up or not (sometimes if they have fire, they can just set the can on it for a minute), so any kind of chef boy rd, dinty moore.... that kind of stuff with pop top cans. Throw a few plastic spoons in with all of that. Chicken also comes in cans and pouches and I like to send tortilla wrappers and salsa with chicken. They can get bread, so peanut butter and jelly would probably be a hit. I don't know if you have Shop N Save where you live, but they do 10 for $10 on a lot of those can foods I just listed.
These units usually also like beef jerky, power bars, granola bars, indiviually wrapped type of stuff they can put in their pockets. Salty is supposed to help with hydration I believe? Individual drink mixes.
Ugh, and how bout a round of antibiotics, yuck with the fingers : P Hygeine wise, baby wipes, baby wipes, some more baby wipes, some anti bacterial anything, listerine, deoderant.
I'm at my limit too for now, but I hope this will help you take care of your guys!
Shelly