You first need to find an old bicycle tire tube. Grab yourself a knife and start to cut the valve in such a way that you do not leave a big hole behind. Then take a wine bottle cork and make it smaller than the valve. This valve should extend just a little from the cork, enough for it to get attached to a bicycle pump.
Now you need to find yourself a drill bit which is almost the size of the valve. In case you can’t find one with the exact same diameter, you can always opt for a smaller one. Drill a hole right in the centre of the cork and press the valve inside the hole you just made. At times the hole is so tight that it is hard to slide in the valve. In that case, get some petroleum jelly and put it around the valve. This will help you easily slide the valve inside the cork. Now, fill one-third of the coke bottle with water and you are almost set to go.
Get some cardboard or wood in order to make a launch pad. Just bury the wood or cardboard inside a hole in the ground or sand and in order to fix it in one place, just put rocks around it. You can also add an angle to your rocket with the help of these rocks. Make sure that you do not point the rocket towards any people or pets as it can cause injury.
Now the cork should be attached into the bottle and then you must fix the pump in it as well. When no one is present around the area where your rocket is, start pumping with the bicycle pump and watch the rocket fly.