I've been a vegan for 25 years or so. My basic menu on tour is:

Morning: Muesli with soja milk or apple juice,
During the day: Peanut butter sandwiches, Bananas or other fresh fruit, Trail mix or peanuts, Orange juice
Evening. Rice and a tin of beans, olive oil and tabasco.

If I find somewhere that sells tofu, or texturised soja protein, then that gets to be a luxury meal. Pasta occasionally...

I eat this day in, and day out on tour, for months on end. Cheap and nutritious. I think I could live on it forever

edit: I cook on a mini trangia, and eat out of the pot.