I'm sorry to say it, and I might even seems like an advocate for fossil fuel (which I don't like to be because I prefer by far electric cars), but cars that run on water simply don't exist. Pure water holds no easy energy, and the only energy you can get from water is by breaking it apart and using its hydrogen, which takes up more energy to make than it can actually give. Burning water does not work, and adding water to fuel/diesel engines simply makes them more inefficient (it is used in some engines but not in general because its uses are rare), so, even though I respect the idea to nut use fossil fuel anymore, I believe that water can not be an answer since it does not provide energy.