Many folks use crackers - lighter and easy for food drops. E.g. vita-weats, but there's a huge range now.
We used to use normal blocks of cheese, and long-life salami/pepperoni (the ones not sold from the fridge) in food drops for the AAWT in summer. We insulated them in the middle of the food drop box. Then after opening, we wrapped the cheese in cheese cloth, then in a plastic bag. Worked well for 3 weeks. Might be dodgy after that. Maybe we used plastic cheese off the shelf sometimes. 'Twas a good while ago...
We also had dried tomatoes (not semi-dried in oil), which you can buy. Vegemite is also good taste-for-weight value. Jam and honey keep well.
Now I go a lot lighter, and use dehydrated hommus. Best to make your own, I think, as a lot of commercial ones use a lot of oil.
And cheese triangles off the shelf (e.g. laughing cow). I use a very small container for the day's hommus, and add water at brekky if I'm organised. Otherwise I just add the water when I get to lunch, shake it around, and it's fine to eat in a couple of minutes.
While I'm dehydrating, I do wasabi dots for a punch of flavour in a tiny volume.
I thought of trying to sprout mung beans or alfalfa along the way, but never got organised enough.
And while it's probably not lunch, fresh oranges and pizza ingredients were favourite food drop treats! And if we could have a fire, we'd add chocolate cake mix and foil, to make cake in the orange skin after we'd eaten the orange. (Cut off the top of the orange, and eat with a spoon.) We did aim to have rest days at food drops if we could.