I usually bring lunch but sometimes "forget" I have it if the cafeteria special looks good. Typical packed lunches for me...

• 8 oz cottage cheese, a Nature Valley oat&honey bar, an apple, and a square of 72% Ghirardelli. I was doing Greek yogurt + fruit cup for a while but it really doesn't compete with cottage cheese nutritionally.
• 2 oz hard sharp cheese from the fancy part of the supermarket, 2 oz dry salami, crackers, fruit, Yoplait, chocolate.
• Leftover pasta & sauce, any description
• "Mexicali skillet" from a 5-ingredient cookbook - recipe 1 lb 93/7 turkey burger + 1 pack taco seasoning + 1 cup of elbow pasta, cooked + 1 can corn + 1 can petite diced tomato, serving size is about a third of the recipe. Good stuff. If you use 80/20 hamburger then the serving is about 1/4 the recipe instead.
• Leftover takeout - Chinese, pizza, whatever you got

I was carrying a liter Sodastream bottle of diet cola for a while - not the regular diet but the free/zero alternate flavor. But it seemed to leave my mouth feeling dry and I've cut it out for now in favor of buying a tub of diet Coke at the cafeteria, with a free refill.