Having been stuck in my car a few times (I normally do a lot of driving for work) my car is very prepped tbh.
In a box in the boot: gloves, socks, hats, yaktrax, water, deicer, scraper, over trousers for me, ready to eat meals (4), self heating flask and heater sachets, hot choc sachets, knork, spork, metal cup, long life sweets in a tin, hand warmer sachets, emergency ponchos, emergency reflective blankets, lantern, power bank jump starter and leads, TravelJane, money (notes and change - there is also money in the compartment in the front but this is last resort), tow rope. Also in the boot are warm waterproof coats and a pair of boots for me. On the dogs side of the boot the floor goes fleece blanket, duvet, picnic blanket, fleece blanket. In the emergency equipment storage thing: comprehensive first aid kit, cpr mask, glow sticks, head torches, hi vis vests, torch, fire extinguisher, reflective triangle.
Glove compartment: book, handwarmer/powerbank, multi adaptor charger cable, cereal bars, sweets, couple of small bottles of water, pen and paper, wipes, tissues
If I was going out and bad weather was predicted, I'd have a sleeping bag and a big flask of boiling water, plus snacks as well. When stuck on a motorway once for 6 hours due to jackknifed lorries in the snow, I was totally happy reading my Kindle, snugly wrapped up and drinking hot chocolate rather than panicking. I didn't have the Travel Jane in the car then which was a bit of an issue!
I know my list sounds huge, but dh and I both go to all kinds of places, and having been stuck, you appreciate the being prepared