For the balloon contraption, you need a balloon, four straws and masking tape. To make the body of the car, you need a 16- to 20-ounce-sized bottle, one straw, four bottle caps of the same size, two bamboo skewers, a nail, a hammer, a knife and a pair of scissors.
Place four drinking straws in a line, and attach them with masking tape. Wrap the end of the balloon around each straw. Wrap masking tape around the balloon tightly to prevent air from escaping.
Use the scissors to cut the straw in half. Attach one half toward the top of the bottle with the masking tape so that the straw is perpendicular to the bottle. Do the same with the other half toward the bottom of the bottle. Use the hammer and the nail to pierce a hole into the center of each bottle cap. Use the knife to cut the bamboo skewers, but make sure that they remain about 1 ½ inches longer than the straws. Place each skewer inside of the straws, and insert each end of the skewers into the bottle caps. Use the knife to cut a slit - about 4 inches down from the opening of the bottle - into the top of the car. Place the open ends of the straws through the slit and out of the opening of the bottle. Inflate the balloon by blowing into the open ends of the straws, and pinch the end of the balloon to trap the air until you are ready to release the car.