I think "cooking" may need a second look. Are you thinking of pots and pans to wash or to stand by them as you heat and prepare ? Or are you thinking about the space a stove & kitchenette would take up in your rig ?
There are alternate ways of heating foods.
A book titled "Manifold Destiny" explains wrapping foods in foil to seal them and laying them on the engine of the rig as you travel. It suggest time or miles it takes to have various foods hot and ready to eat. (with no more trouble than mixing ingredients in a can and stirring).
Manifold Destiny
Solar Ovens can be built out of corrugated box board such as old boxes. You just mix up your ingredients and sit the solar oven in the sun and wait while that food bakes. With the way you are stirring up some of this stuff yo are half way there anyhow.
Some ready to eats I'm mention
Canned Sardines or Kippered Hearing
Apple Sauce
Olives
Figs
Dates
Avocados or canned Guacamole
Humus if you have a can of chic peas, olive oil, garlic salt and a battery hand blender
Powered whip cream again using water and hand blender and this used with canned fruits
(this mixed with mayo and or some cream cheese warmed in the sun and blended well....using the cream
cheese as soon as purchased so no refrigeration is required)
You may do without refrigeration but some form of heat may greatly improve the health and safety of the foods you
would choose to eat.