Using empty Gatorade or other plastic bottles, you can build model rockets that actually take off.
There are many different kinds of bottle rockets, including alcohol or "whoosh" rockets, and water rockets, which use a jet of water powered by compressed air or gas. Common household substances such as baking soda, lemon juice and vinegar can all be used to get lift-off.
Cut one of the soda bottles in half. Cut two strips of construction paper an inch or two longer than the circumference of the intact bottle. Wrap each strip very loosely around the bottle. Fold the ends of each strip together and secure the loops to themselves with tape. Remove the bottle from the loops. Tape the ends of the two loops of paper to the dowel or garden cane with one at the top and one five or six inches lower. The loops should be horizontal when the dowel or cane is standing upright.
Take all of your items outside. Make a hole in the ground and place the bottom half of the cut soda bottle into it so that it is stable.
Stick the open end of the dowel or cane into the ground next to the cut bottle so that it is vertical and the hoops are positioned over the cut bottle. If you can't dig in the ground, set the cut soda bottle on a flat surface. Steady it and the dowel with rocks or bricks. The cut half of the bottle and the paper hoops are your launch pad and launch rail; they will hold your upturned bottle rocket steady.
Mix a tablespoon of citric acid crystals with a cup of water in the measuring cup. Alternatively, measure a cupful of vinegar or lemon juice. Place a teaspoon of baking soda in the middle of a paper towel. Roll it up into a small parcel.
Hold the bottle right side up. Pour the citric acid solution, lemon juice or vinegar into the bottle. Push the baking soda parcel into the neck of the bottle, but not all the way in. Put the cap on the bottle and fasten loosely.
Turn the bottle over and very quickly slip it through the paper hoops and into the cut soda bottle. Stand well back and wait for your rocket to launch.
You may need to fine-tune your rocket before it works satisfactorily. Try thinner or thicker paper towels, stronger or weaker acid solutions, more or less baking soda.
Bottle rockets can hurt you if they hit you. Stand away from the rocket. Never launch the rocket indoors and never point it at people, animals or vehicles.