I have 3'x1.5'x1.5' in cubic feet of space dedicated to food storage on the truck, and both cubbies between the side box storage and cabinets under the bed are dedicated to water. 3-5 gallons in 1 gallon arrowhead screw tops for dual purpose, and a flat of bottled. With a real fridge, I'd eat off the truck even more as Target/Walmart all have precooked foodstuffs that just need refrigeration, and a butane stove for catwalk cooking wouldn't be that big of a deal for fresh steaks or the like. My coleman cooler isn't up to the task of maintaining good temps without my ducting, and I pulled it off when I swapped for 2 weeks to a freightliner when my normal rig was in the shop. Haven't put it on, as winter's necessitated defrost and heat use, so it's just a drink cooler and condiment storage for the season.
I prefer the 12v crockpot to the lunchbox cooker since it's got a switch on the pot and I can set it up so I can reach it from the drivers seat, turn it on an hour out from stopping after having put a can or two of soup or spaghetti in it at lunch. The water heater lets me ramen it up if I'm in the mood for something quick and warm before bed, usually before my "splurge day" of off the truck food on a fuel & 30 or if I shut down at a truck stop.
I only eat a meal from off the truck once every two days or so, unless it's an impromptu "Damn that smells good" perfect storm like my last week's delivery in portland.... rolled past a prime rib joint I smelled with the windows up from a block away.... and was blessed with a drop and no empty hook, so I bobtailed my happy butt over to get me some high grade nommage since I fit in the parking lot bobtail, and my pickup window was 1400-2100, with my drop being at noon. Great staff, great service, GLORIOUS food.
Winning.