Those 100 calorie sandwich thins (if they have them where you are), deli meat (low sodium if you worried about salt intake) and reduced fat cheese are good. I can make a nice filling sandwich for around 250 calories. Add a little lettuce and some tomatoes that you slice up and put on when you're ready to eat. I like to make sandwiches with some flavored cream cheese. It has a lot more flavor than mayo and some of them are lower in calorie per TBS than most mayo and you can skip the cheese too. If they don't have the sandwich thins, a tortilla works too. Herb and garlic cream cheese with spinach and turkey is my favorite, tuna salad mixed with some chopped fresh spinach is a close second. I also like tuna and hummus in a pita, lots of protein.

When we go on long car trips, we usually pack a cooler with pre-cut fruit and veggies, Tupperware bowls of individual salads, 100 calorie packs or nuts and other snacks and of course, plenty of water.