I work 12-16 hour shifts. I usually fix a PB sandwich with a cup of broccoli, carrots, cucumbers, and/or bell peppers on the side for lunch. Another go to is a veggie wrap or sandwich with bell pepper, shredded carrots, spinach, alfalfa sprouts, mashed white beans, and avacado. I usually will make 2-3 days work at a time so I can just grab and go. Snacks usually consists of Luna Bars occasionally, fruits and nuts often, soy yogurt occasionally, but mostly fruits and nuts.
When I was in college, I would be on campus from 7am to 10pm, since I had two part-time jobs there plus classes. So I'd put breakfast, lunch, and dinner in a compact purse-sized cooler bag everyday. This might sound kind of boring, but this is what I brought:
Breakfast: packet of instant oatmeal plus a cup and spoon. You can get hot water from a cafe, and then mix it up there.
Dinner: another PB&J or hummus sandwich, salad in a small tupperware (put dressing in a small baggie and tie it in a knot, then put it in the tupperware)
Snacks: trail mix (I loved combining dried apricots with dark chocolate chips and plain almonds), pretzels, or cliff bar, + whatever I didn't eat from the other meals
All of those things can be prepared the night before. Keep it all in the fridge in a bag and then grab it before you leave for school. You can wash out your containers and utensils in the restrooms so they don't get your backpack all smelly. Oh and if you have something that tastes better hot, you can ask a cafe or even someone in a dorm or lab if you can use their microwave for a nominal fee, if any.
I wasn't vegan at the time, but I ate like it! All the foods that spoil and foul up your backpack are the omni ones: meat, cheese, yogurt, tuna, anything with mayo, etc.
Snacking helps you remain active and alert between breakfast, lunch and dinner. Choose snacks such as fresh fruits, nuts, popcorn, veggies, chickpeas and almonds they are compact enough and can fit in your bag easily. Stay away from sodas, chips and other kinds of junk food, they are really harmful for your body.