In my POS Jeep at all times for mystery shopping:
LOAs and leave behinds for all of the revealed gas station audits
a multiport quick charger (3 USB and 2 Type C ports)
2 gel pens, and a handful of ball points that I can never find.
2 sharpies, different size tips.
a full change of clothes
a heavy duty plastic zipper bag with a handful of tea towels, some bandanas, handkerchiefs, and a couple of the tube things I cover my hair with.
3 traffic vests, mine, my son's, and my hoody with the reflective strips for when it's cold.
2 spare empty refillable travel bottles so I can buy soda without having to use Styrofoam, and some meal containers for the same purpose. (Styrofoam is NOT welcome in my home and this will soon be followed by most types of plastic).
When I walk out the door I take one or two 34 oz of bottles of home filtered water.
My butterfly bag with my CD's, tablet and phone/wallet and a couple extra bandanas
My purse, with two emergency flashlights, aspirin, stronger pain meds, Listerine strips and hygiene stuff, toothpicks and dental floss.
And if I'm doing gas stations that I'm allowed to buy more than one gallon of gasoline at, I carry one gas can for every 2 shops over the POS Jeep's gas tank capacity. Because we don't waste an opportunity for free or extra cheap gasoline. Right now I'm slowly replacing all of my old plastic 5 gal. gas cans with steel jerry cans (they take up less space, and they don't leak).