You may find that it is convenient to have lunch in your pack. You can stop any time and any place. Buy bread fresh daily; it may dry out in a day. Cheese, sausage, and meat are available in all the little shops. Meat should be consumed fairly promptly. Canned foods like tuna and pate make a good lunch. Bananas keep your potassium level up, and other fruit generally keeps well. Merchants do not want you to handle the produce, so ask for help in the markets. Point to what you want if you are about to get an aging apple!! On the theory that yogurt is produced at room temperature or higher, I buy yogurt and keep it several days in my pack. The squeamish may not want to do that. Eggs are sold in a four-pack, so you can boil them in the evening and have hard boiled eggs for protein. I keep them several days in my pack against all the safe food handling recommendations. I would not do that if I punctured the shell to hard boil them.
Buen provecho.