Some people live out of their cars! I personally am not one of those people but there are things that I have learned to keep in my car that I know have helped me and that makes me feel way more comfortable should something happen.
Keep in mind that much of this depends on your climate too. People in the desert are going to need a snake bit kit more than a snow shovel and vice versa. Though it can hurt to have both in the mountains out here.
Your cars Manual IN PRINT: Your cell phone might not have connectivity everywhere (I know, that’s a strange concept) and you may not be able to look up how to on youtube. Fear not! There used to be a book for that! Its called a manual and every car comes with one.
A Car Jack, a donut (Spar) tire, jumper cables: And ladies you need to know how to use it too! There are also kits to patch your own tire which are highly useful until you can get to the next service station too.
A Tool Kit/ Multitool: Should something go wrong you are going to want to have one of these there. Make sure that it includes a fully charged flashlight, hammer a multi-head screwdriver, a wrench, work gloves and duct tape. If you’ve got or can get a really good multitool I would go for that too.
A blanket: Ever been in a snow storm and your car dies? It sucks. Even just on very long road trips it can suck so make sure to keep a blanket in your car.
Water/ energy bars: You can drink it, yes, but you can also use it to cool down areas of your car should they overheat. Energy bars go without saying. You should have something to eat in your car just in case.
A First Aid Kit: A lot of this depends on where you are but a basic first aid kit is a must. A snake bit kit never hurts either. Also, make sure that you have instant ice packs which only take a crack to cool down. If anyone driving with you has allergic reactions to anything in the wild this is probably a good thing to have too. I personally have one stocked full of bandaids and what not for my running injuries too.
USB charger for your phone: So much of our lives are on our phones now, including GPS. Make sure you have one tucked away or a jump battery for emergencies.
For nonemergencies, it’s really up to you but I personally have a few items that I always keep ready to go. These are more or less up to you based on your lifestyle but I would recommend at least some of them.
A change of clothes: a lot of my running takes me to places where I might have to make a quick change. No one wants to go to a post-race dinner in their sweaty smelly clothes. Plus its just super uncomfortable. This actually can be a survival item too seeing as if you get drenched in the rain or snow its not a good idea to sit around like that.
Dog Bowl: for the fur baby. Don’t forget that they need to hydrate just as much and sometimes more than you do.
Hygiene Products: Both Feminine and otherwise for when the rose river decides to make an unexpected appearance.