I have been feeling your pain for years now. Here's what I've been doing:

For breakfast, you can microwave eggs. Not the best texture, but cover it with cheese and hot sauce and throw it down as fast as possible. You can microwave bacon if that's your thing, or there's precooked sausage patties. Some of the breakfast burritos they have in the freezer near the breakfast section aren't too bad and fairly cheap as well. Also, there's like a million combinations you can make with oatmeal. Fruit, nuts, ect. The possibilities are endless. Just look around the internet for inspiration.

For lunch and dinner, I recommend buying rotisserie chickens. I've yet to see a commissary where they were expensive. Shred the meat up in a Tupperware container and you can get a few meals out of each one. Also, Tyson makes frozen precooked chicken in a big bag. They have white and dark meat. All you gotta do is microwave it. I never looked up the cost comparison, but there's that. There's some precooked steak pieces somewhere, but it's a little pricey. I get those breaded chicken patties every once in a while just for something different.

There's plenty of instant rice, mashed potatoes, pasta, and steamer vegetables you can mix it with that only require microwaving. You can bake white and sweet potatoes in the microwave. Sometimes I'll just throw a handful of kale or spinach in a bowl with the chicken. You could use tuna for most of this as well. Honestly, canned chicken isn't the worst thing I've ever eaten, but some people swear its just cat food. Hot sauce covers up everything if you use enough of it. There's salmon in those packages as well if you're into that stuff.

Evaluate how much you enjoy eating a sandwich. I'm going to share my secret on sandwiches with you. Unless you're stationed at Auschwitz, you're allowed an iron. There's no way a military barracks wont let you own an iron. Go get a cheap one. While you're out, get some tin foil. Then assemble your favorite sandwich. Put some butter on the outside of the bread, grilled cheese style, if you're into that. Wrap that baby in tin foil, stick the hot iron on top of that. It really makes a difference after a long time of eating the same stuff.

Finally, TV dinners have come a long way since you were a kid. They're really not that bad any more. Marie Callender's has some really tasty stuff. Boston Market is a close second. Stay away from Banquet. There's a reason it's $0.89 each.