Drink cold water or other beverages. If you have ice water on hand and can keep a cooler in the car, keep your body cool by drinking plenty of chilly beverages.
Fan yourself with a newspaper or magazine while you're riding in the car. This obviously won't work if you're driving. If you are the driver, have a passenger fan you to cool your body.
Apply cool compresses to your face and body. Keep a cooler full of cold compresses or ice in the car. Place the compresses on your forehead and under your arms to keep your body temperature down.
Turn the fan on in your car and place ice packs over the vents. The air will blow out and the ice will cool the air and act as air conditioning.
Eat lightly when you plan to spend a lot of time in your car without air conditioning. Big, heavy meals tend to raise the body's temperature. Light meals will keep your body from having to work harder to digest the food and this helps keep your body temperature low.