Re: What chemicals can create a reaction similar to baking soda+vinegar?

Although the baking soda/vinegar chemical reaction is a very weak and harmless one, trying to modify the concept to come up with something more powerful and energetic can be very dangerous. I could suggest several such reactions that create gases and can hence be used for propulsion but the problem with most of them is that either the chemicals themselves or the end products are very corrosive and/or toxic (as a general rule if two things react vigorously than there is a good chance at least one of them is not a very safe chemical to play with). Also there is the problem of obtaining the chemicals in the first place, which most people outside the chemistry field find very difficult.

My suggestion for you if you are looking for a higher powered solution for water bottle rockets would be to try a cryogenic expansion engine. If you drop liquid nitrogen or carbon dioxide (well, CO2 is not really cold enough to be cryogenic, but the concept is the same) in water the phase expansion (solid / gas or liquid/gas) and the thermal expansion (from -196C (LN2) or -89C (CO2) to 20C or whatever the temperature of the water is at) will cause it to expand dramatically (880.15 times the original volume in the case of LN2. I never bothered calculating it for CO2 but it should be in the 600x range). That expansion will provide you with all the pressure you could ever need. In fact, I strongly warn you against trying this with anything other than corks in the bottle, as there is no way that an ordinary vessel could hold the final pressures that could be reached from even a partial LN2 / CO2 charge.

There is quite a good deal of information of cryogenic engines, cryogenic fuels, and experiments with Liquid Nitrogen on my page. I even have a picture of my Liquid Nitrogen rocket powered car there. Please check out http://www.powerlabs.org/

If you really want to try doing this the chemical way, using a couple squirts of an alcohol-based hair spray inside the bottle and igniting it with a spark gap would provide you with a very high instantaneous pressure rise with no harmful by-products. Be aware though that it is VERY loud (read: sounds like an explosion) and not exactly the safest thing to do... To speed up the speed of the vinegar/baking soda reaction you could try substituting the vinegar for something more acidic, such as a dilute acetic acid solution or even dilute battery acid (Sulphuric Acid). The problem with that is of course that when the cork pops you get a spray of acid that will burn clothing and skin in a rather unpleasant manner.

Good luck, and play safe!