I keep one of those Ozark Trail 26qt coolers strapped behind the passenger seat on that little folding thing Toyota calls a jump seat in the Access Cab Tacomas (I mounted some footman's loops and have two straps over it); there are a couple of gallons of water in various size bottles (whatever is on sale at the grocery store when I need to buy more). Some of them have been in there over a year including when the outside temps were below freezing with no issues. They're in the cooler to help keep them from freezing or getting too hot, to keep them stored together and, in the event of an accident, so they can't fly around the cab and if one or more were to leak I could just dump the water out or use it if I needed to.
Food stays in containers in the back; the truck has a camper shell and essentially stays set up for minimalist camping year round unless I need to carry larger items. Canned stuff stays in a Rubbermaid tote (I want to say they're the three gallon size; I've got four of them stacked back there with various camping stuff stored in them). I don't normally eat much canned food but things like Chef Boyardee and non-dairy based soups will keep well past the date stamped on the can even with the temperature changes. My truck is black, the camper shell is black and it's common for us to have temps in the 90s for several weeks in a row in the summer. I also have a metal storage tin, just a rectangular cracker type can with snug fitting lid, that I use to store stuff that's in soft packaging that I don't want rodents or insects getting to. There are a couple of packs of various flavors of tuna, some pulled pork that someone on here recommended, some freeze dried foods* and soup and noodle packs, packs of instant coffee and things like that.
I'm not recommending anyone else do it, but I've eaten tuna and other food that been stored in the truck well past the dates on the packaging and never worried about it as long as it didn't smell funky and the packaging was in good condition. At any given time I could stay a couple of days to a week in my truck with no problem. One of my older water filters lives back there too so if I have access to water I could stretch the time frame out a bit.
There are two 1# Coleman propane bottles, a couple of Jetboil type canisters, a Jetboil stove and one of those tiny Chinese stoves in the truck; if I'm actually going camping I'll carry a better stove that I can actually cook on. Seasonings do start losing their flavor so I'll rotate them out but I've got one of those camping kits with little tins of various seasonings that stays with the other cooking equipment.
I rarely carry extra gasoline except when I'm going out west and then I'll carry a NATO can; never had any issues with them either as long as the seal is intact and I sleep back there. I'll carry more food and water if I'm going camping- and stuff I actually like to cook and eat. Again, not recommending anyone else do what I do, just saying it's what I've done since the late eighties. I used to be a lot more diligent about rotating foodstuff but I quit worrying so much about it years ago and, knock on wood, haven't gotten sick yet.
*Side note, Readywise Emergency Food is practically inedible, even when it's fresh off the shelves it's some of the nastiest I've tried.
Practically all of the freeze dried stuff has way too much salt, just something to keep in mind if you're sodium sensitive or just don't like salt.