Drop a few smell good wax cubes in a jar, and screw on a top with holes. Place in cupholder of your car. When your car heats up from the summer sun, the wax melts and you have an instant air freshener!
How to keep your car smelling nice? Check out this great tutorial that explains how to easily create natural air fresheners and don't forget to visit the collaborative board "DIY bloggers for Volkswagen" for more inspiration: http://www.pinterest.com/volkswagen/diy-bloggers-for-volkswagen