I've always had a microwave at work but I'm considering using a soup thermos of some sort to take hot porridges and lentils/dal type of things with me so I can eat them on arrival, it's more of a winter thing doing it hot, but you can make cold museli (raw oats + nuts/fruits/etc. of your choice, likely cheaper portions if you make big batches) and just let it soak up milk/jus and eat that when you get to class. You'd likely have to to start out with a lot more milk than you normally would if you just made fresh museli and ate it right away.

I've also taken a liking to cold burritos, they are easy to make in large quantities at home and a few can pack in the calories, depending on how you make them. I make vegetarian ones and use whole-grain tortillas usually, they seem to keep better as well. Dry beans and a pressure cooker can save lots of money too. Hard boiled eggs make good snacks too. Big tubs of plain yogourt can be mixed up with some jam and packed in a small nalgene or mason jar. Bagels, apples and oranges end up in my bag too, nice portable snacks. Stews and curries can also travel well and be made to whatever dietary needs you have.

Oatmeal is one of the easiest things. Not the sugary stuff mind you but the natural plain stuff. You can add whatever you want to flavor it. I add whey protein and then it tastes like whatever flavor I put in there. I throw in some ground flax too for EFAs.

If you end up biking on an empty stomach you should at least take some powdered BCAA mix in my opinion so your body has those available and doesn't need to break down any muscle tissue.