One of the hardest needs to satisfy well on the road is keeping clean.
Important Health Note:whenever you use public facilities, make sure you wear foot protection and touch as little of anything as possible. The recent outbreaks of antibiotic resistant staph and skin infections were all acquired in public facilities.
If you can afford it, get a membership at a gym. For between $20 - $50.00/month, you'll have daily access to a hot shower and gym equipment.
Flying J, Pilot, T/A, and other truck stops offer showers for $7 - $9 (current prices in 2007).
These are good for occasional use, but I always felt uncomfortable using them. It's pretty obvious what you're doing in the bathroom if you go in there bleary-eyed and unshaven, and come out clean, shaved, and well-coiffed. If you can
"Dundo"/ Sponge Bath method
This is the least water consuming method, and is the easiest method for keeping clean if you're living in a car or other small space.
You can keep reasonably clean at minimum, you will need about 1 quart of water. Heat half the water to boiling on a camp stove. Pour about a 2 cups of water into a bowl, and add a enough cold water to make the temperature comfortable. Wet a small dishrag or sponge with the water. Take off your top, and drape a towel over your shoulders. Wet your hair with the dishrag. Pour a small droplet of soap into your palm and work it into your hair. Repeat until you have a lather. Use as little soap as necessary, so that you don't have to use much water to rinse it out. Leave the soap in your hair to soak while you lather up your face and torso. Bend over a bowl, and pour water over your hair so it drains into the bowl.
A plastic bladder which is clear on one side and black on the other. It can be placed on the dashboard or anywhere in the sun to warm the water. Hang it from something(a tree or part of your van) and the water flows through a tube and out through a shower head. If you prefer to shower outside of your van be sure to find a secluded spot such as behind a grocery store or strip mall. Showering inside a plastic rain poncho can prevent indecent exposure. Fast drying travel towels composed of synthetic materials are available and often preferable over slow to dry cotton towels. Nearly identical towels are available for a much lower price in the automotive or housecleaning section of most grocery and big-box stores.
Built-in Heat Exchanger
Several systems exist for hooking up a hot water heater to your automobile's cooling system.
There is a commercial product for showering in a vehicle. Its a little spendy at $300. You can find it at http://www.truckshower.com