Dunno about everyone else, but I find a hot dinner in the winter to have a civilizing effect. So I have hot meal ideas.
1) Thermos! Get a good vacuum-sealed one and pack with soup, chili, pasta, casserole, etc. Maybe take food out and reheat at work if you have a microwave, then it only has to stay warm while you're at the gym. If you don't want to mess with all the above, just a mug of tea or coffee can do wonders for an otherwise sad sandwich.
2) Gas stations will give you free hot water if you ask. This opens up options for tea/coffee, oatmeal, and once again soup. You could try combining frozen veggies+precooked chicken+possibly noodles or rice, adding a spoonful of Better than Boullion, and filling that up with hot water. Might be able to get warm soup.
3) If I ran a Bible study, I would probably not mind if someone showed up 20 minutes early and used my microwave and ate their dinner (if they arranged it ahead of time politely). Assuming I was home, etc. Part of the Mustachian lifestyle is building and using your community. But of course this depends on individual circumstances. But I would ask.
To all those advocating hunger: not a great option if you need to go grocery shopping, exert yourself physically (lowers blood sugar), exert yourself mentally (you lose focus), or demonstrate any kind of willpower. You can get through it occasionally, but it shouldn't be a strategy on a regular basis!