This is a rather amusing home made toy somebody showed me many years ago.

Get a two liter plastic beverage bottle, empty, and keep the cap. Make sure it's rinsed out and dry inside. Drill a 1/4" (7 mm) diameter hole in the center of of the cap.

Next you'll need some sort of ignition device. I've seen these touched off with matches, but I _DON'T_ recommend that unless you like burned fingers and singed eyebrows... :-/ I made a remote igniter with a "push button" piezo electric starter for a gas (propane) BBQ grill, some scrap wire, a small ceramic insulator, and some black vinyl electrical tape. The piezo starters can often be found as a replacement part in hardware stores, and at many places that sell and service gas BBQ grills. My starter is pictured in the foreground. I stripped off the insultaion from the wires at the end that goes into the hole drilled in the cap, and the bare wires separated by about 1/8" (3.5 mm) to produce a spark gap.

Next, get some 70% isopropyl alcohol. It's readily available as "rubbing alcohol" in the over-the-counter medicine section of grocery stores, "dollar stores," pharmacies,etc.

Remove the drilled cap from the soda bottle. Pour just a little bit of alcohol into the soda bottle. Better yet: if you have an eyedropper left over from some used-up medicine, squirt about 1.5 eyedropper fulls into the bottle - it's just about the ideal amount. Put the caps on BOTH bottles, and then swish the alcohol inside the soda bottle until it evaporates completely. Put the spark gap inside the hole (or lit match up to the hole, not recommended). If all goes well, the alcohol vapors will ignite, and the soda bottle will shoot off at high speed with a LOUD hiss. BE CAREFUL and plan ahead - these things have minimal aerodynamic stability, and can take off in unexpected directions.

The cap can be left off, and the bottle will still take off when the alcohol vapor is ignited. However, it'll only go about two or three feet (60 to 90 cm), and the exhaut will produce a LOT less noise.

The bottle itself will get warped due to the heat, but should last for at least two to three shots (or more) before losing too much volume to shrinkage.

This is the sort of thing that should be done outdoors, away from pets, with a water hose and first aid handy... ;-)

Not a pub-blues band, but another John Barber creation. Sadly missing the electric assist, after an 'exciting' previous flight. This really went some on a 38mm Contrail hybrid motor. Nitrous pressures were high due to the warm weather.