go to the home goods store and get one of those things you hang on the wall to put shoes/slippers in.
cut it in half so it's half as long, hang it on the inside sides of your vehicle or on the back of the door.
use it as storage for odds and ends. toothbrush/toothpaste, deodorant, flip flops, etc just random shit.
invest in a good quality esky/cooler. if you use it right it'll keep shit cold for a week before you need to replace the ice in it.
get an old paint/chemical bucket with a sealable lid, pack biodegradable garbage bags with it. use it as a back-up or emergency toilet. you may never need it but when you do you'll be glad you did.
invest in a portable camp shower, or in a pinch hang a plastic bag from a tree, fill it with warm water and pinch a couple of holes in the bottom. portable camp shower shouldnt set you back more than $30 at the store though, it's essentially just a canvas bag you hang from a tree branch.
get one of pic related, keep the air circulating through your car during the day. under $20 at Super A-mart.
other than that, pack basic normal camping gear and maybe invest in a hammock as well. when the weather's warm and dry sleep in the hammock outside, just throw a mosquito net over you if there's mozzies around.