There is no way to run your car on water. The advertisements with the hydrogen converters (browns gas... etc.) are a scam that rely on your ignorance of physics and chemistry. Billions of dollars are being poured into technologies to make hydrogen (water powered) cars viable and the technology is coming along. It is not, however, availabe for your gasoline vehicle. If you spend one penny on a system that claims this, you have just thrown a penny away and probably done damage to your car.
I wrote a satirical hub on it explaining the nature of the logic behind it: