What you eat can vary so much according to what your pref’s are for food, time and energy expended in cooking. My long tours (2 weeks to 3 months) were a very long time ago but I did the following:

Breakfasts were things I could make easily by boiling water or in a fry pan, as well as yogurt and granola. I usually bought anything perishable the evening before, kept it cool in an insulated lunch bag inside my pannier. Of course I always had food accessible from the saddle and ate often during the day.

Lunch was typically cold unless I splurged on a low cost lunch at a diner. I generally ate sandwiches – meat and cheese, tomato if I had it. Sometimes I found reasonably priced potato salad and made a sandwich out of it. I bought breads that were substantial so as to hold up better – especially things like round or half-round ryes or sourdoughs because the shape was good for panniers.

Dinner varied quite a bit. I often ate from the food I carried all the time, which was as compact as possible – pasta, dried fruit, homemade turkey jerky, etc. I often bought 6 eggs (almost any grocery will allow you to split a dozen pkg in half). Used some in either the evening or a.m. and boiled the remainder for snacks or for egg salad. (The heaviest food item I kept in stock was Miracle Whip). I also carried a small amt of oil, romano cheese and herb/spices.

I always tried to keep my food stashed away from the sun and with clothing around it to keep it cooler. On tours in very hot weather I’d ask for some ice cubes when I ate in a restaurant and put them in a freezer bag. If I stayed in a hotel or was invited to a home overnight I froze a small juice bottle for additional cooling.