Face it; our cars can sometimes reek. They seem to absorb almost every scent that enters them, especially fast food. Nobody likes driving around with the stale odor of greasy burgers hanging around. You could get one of those pine tree air fresheners, or you could make your own.
Put some scented candle wax into a jar that also has a lid. Make a few puncture marks on the cover, and screw it on tightly. The jar should easily fit into one of your cupholders. Then, when your car heats up, the wax will begin to melt and release the scent. Just make sure you didn’t choose greasy hamburger-scented candle wax!