When canoeing on multi-day trips, I picked up some nice tips from other people, some really stuck. You want food that won't spoil, has minimal clean-up, and packs flat and light weight. I don't want to kill the earth, but there is a time for doing dishes and it isn't when I could be spending my time fishing instead, so I use more disposable food packets on trips.
Here's a great way to pack tuna sandwiches that don't spoil, get squished, or take up much space or weight.
1/2 package of flat buritto size tortillas
1 foil pouch of tuna, not cans - there is little extra water and no bulky metal can
Use mayonaisse condiment packets - no need to worry about refrigerating or icing the remainder.
Pickle relish packets
Salt & pepper packets
Just lay about 4 tortillas out on whatever constitutes a clean surface by your camping standards, and squeeze contents of all packets onto the tortillas. Dust with salt and pepper packets, and roll them up. Whallah!
I put everything needed for one meal (feeds 2 guys if using the above recipe) into a gallon size zip-lock, and keep it somewhere handy until you are ready to make it. The best part is there's no dishes to clean, and very little trash to pack out.