Potatoes are a great source of carbs, they'll fill you up, and they are DIRT CHEAP. Keep a few rolling around in your cab at all times. Plenty of recipes use em, and they stay fresh for a long time. This recipe is super easy, but you will need a hotplate/cooking stove with a frying pan as well as a microwave.
This recipe does require a grater to shred the potatoes, but the one I've linked to is nice and compact and should fit with the rest of your kitchen gear, and you'll be able to use it for a bunch of other dishes as well.
Shred 1 russet potato onto a few paper towels. Spread out the potatoes, and sandwich them between a few sheets of paper towel to press out as much water as you can, this will help them get nice and brown and crispy. Soggy hash browns are terrible.
On a plate, microwave your pressed potatoes for about a minute and a half to 2 minutes.
While the potatoes are in the microwave, heat up a tablespoon or so of olive oil in your frying pan until it's runny and shimmery. Add the potatoes, and spread evenly and press into the pan. Cook for a couple minutes until golden brown on the bottom, and flip to cook for another 2 minutes.
Add salt and pepper and lots of hot sauce or some ketchup!
1 russet potato
1 tablespoon olive oil
pinch of salt and pepper