My friend asked me a few weeks ago (sorry for the delay) to look into figuring out meals that could be packed that wouldn't require a refrigerator or microwave once taken out for the day. She's got days jam-packed with school and nowhere to prepare meals; she'd also grown incredibly tired of sandwiches of any shape and form. I had done the research but kept failing to post it so I figured it'd be a good idea to do it on her birthday. Happy virtual birthday gift! Hope this helps =]
Equipment & prep
Things that will be your friend are a thermos, insulated lunch bag, ice pack, tupperware, and plastic wrap. To use your thermos smartly, pre-heat it by filling with hot water the morning of when you get ready to go wherever you're going. Then dump out the hot water and put in whatever needs to stay warm. It should keep until you eat! As for when the heck you're going to have time to do these things, strive for the weekends or the night before. Make several prepped lunches on days when you are less swamped with work so you don't have to worry day-to-day.
Sandwiches and wraps
Yes my friend got tired of these but you can't deny that they're one of the easier foods to make for packed lunches. You'll have to have to learn to switch it up a bit with the fillings. Keep in mind that if you're going to be without refrigeration all day, mayonnaise and other like spreads will spoil quite easily. Be careful of what you put in with them. To avoid soggy sandwiches, you can pack your vegetables separately or toast your bread on the inner sides. Mix it up with the type of breads you'll be using - sliced bread, bagel halves, flatbread, tortillas, etc. Though technically not a "wrap," I've found that stuffed grape leaves are small but pack a delicious and filling punch too. You could also try non-raw sushi or onigiri.
Salads
We're using this term loosely here. I had mentioned earlier not to use perishable spreads so ranch dressing and such are not the best to think about. Pasta salads are a good choice here (tortellini salad, rotini salad, couscous, etc). I liked having rotini tossed with peas, carrots, lemon juice, and olive oil back when I was in school. With caution to the weather, you can also bring potato/chicken/tuna salad with you and some crackers. Try tabbouleh (had a lot of this too!) which is an Arab salad made of bulgur, tomato, cucumber, parsley, garlic, olive oil, lemon juice, and salt. How about a caprese salad of mozzarella and grape tomatoes? Chickpea salad?
Crackers & accompaniments
If you don't like crackers, you've got other choices such as flatbread, crispbread, tostadas, tortilla chips, pita chips, pita bread, and crostini. Pack some cheese (Babybel - good for individual portions, Laughing Cow for spreading, cheese cubes, string cheese for snacking, etc) or dips (hummus, white bean dip, salsa, etc). True, this won't be the most filling part of your meal but it's a good quick eat in between bigger meals. You could even make your own "Lunchables" by slicing up meats and cheeses beforehand. Try salumi (dried) with your food or even canned tuna/salmon/chicken.
Fruits & Vegetables
A healthy go-to, fruits and vegetables can make life easier. There are some that you can bring whole but some that you can also slice up the night before (lemon or saltwater will keep from browning). Some examples of fruits to tote along are apples (with caramel dip maybe?), oranges, grapes, bananas, melons, tangerines/clementines, berries, mango, pineapple, grapefruit, peaches, and watermelon. Don't have fresh fruit on hand? Get some healthy individual fruit cups or even applesauce. Dried fruits are delicious as well. Don't forget juice boxes (just be wary of added sugar)! For veggies, try sugar snap peas, edamame, green beans, celery, broccoli, and baby carrots. Marinate some mushrooms to pop into your mouth.
Breads & dried goods
Carbs for energy! Without getting into the different varieties of breads, keep in mind that muffins and bagels can be your filling friends. There are also hearty flavorful breads that will keep you feeling more stuffed than plain ol' white such as banana, pumpkin, or even raisin breads. Cornbread is a nice accompaniment to a meal. Heck, you can even bring pancakes and waffles with you! Pasties of any kind will do whether fruit or meat. To get more adventurous, pack cold soba or buckwheat noodles to slurp up. How about seasoned polenta, tempeh, or fried tofu? Falafel's a nice change as well as pan-fried risotto cakes. For dried snacks, look to trail mix, granola, jerky, and nuts.
Heated foods
This is where the tip with the thermos comes in handy. Fill it up with hot water while you're getting ready in the morning and then empty before popping in your food. You could have any type of soups in your thermos or hearty chili. Stick boiled eggs in there (which can also be had cold). Put tamales or enchiladas in the cozy container. Chicken cutlets or grilled chicken breast? Baked potato? If it fits, it'll be good!