Really whatever works for you. I do find nuts hard on my stomach first (thats probably a me thing), but if you feel ok, its totally fine. Most days its a salad, crackers, yogurt & fruit, todays its gonna be pizza though lol
Just a suggestion:
A handful of “raw” almonds, an avocado and one of those single serving cans of pineapple juice…and just keep a thing of garlic salt in the truck to sprinkle on the avocado after you slice it - which you can do with the handle of the same plastic spoon you use to eat it, in a pinch.
When I was hiking ten miles a day - in a different life before I gained 70lbs - that was my go-to trail meal. You can swap out the avocado for a greek yogurt if you have an insulated lunchbox.
Edit: These days I have access to a kitchen at lunch and I make homemade miso b/c of the probiotics, the choline and the fact that it clears out my guts about 45 minutes afterwards, lol.