I probably carry waaaay too much gear in vehicles, always........way to much to list.
This is part of the layered approach to a BOB.
In the days of not really being able to fix stuff on vehicles, save fuses, leaks, flat tires, and maybe getting stuck, a good "kit" on board is important to me.

Gear is check/adjusted on the spring forward/fall back check , strating with re-setting the clock, checking batteries on flashlights, radio's ....and adding water or removing water....on board water filters are always there.
Plastic bottles of "Heet" purchased on sale, can last a long time for fueling the achy stove.

P.S. I always keep fuel tanks full as part of the BO preps.........

This is just from personal experience being in vehicles with battery issues, and YMMV, but my husband and I have routinely kept a spare battery and very heavy duty jumper cables in our vehicle. That way, if something ever happens, and the battery runs down, you don't have to try to flag down someone else to get your battery back up. You can either jump straight off the battery "in the back," or you can just switch them out as needed, and get them both recharged. Comes in very handy even when TS hasn't HTF, just in terms of camping trips, or stupidly leaving your interior lights on for too long. Hopefully this is not a "duh" post, but hey, .

Excellent information.

The denatured alcohol sold at Wally World etc is excellent alcohol stove fuel, and can be stored in 20oz water or soda bottles. Just be sure to screw the lid on very tight, this stuff is hygroscopic and becomes less useful quickly if condensation in the bottle can occur.