There is a video online that shows the Japanese has invented a motor car that runs on water which is H2O, 2 parts of hydrogen and one part of oxygen. The car has a battery that converts water H2O into Hydrogen and oxygen. Hydrogen can burn or combustible easily which moves the car. When the battery is flat it needs to be charged with electricity.

I think this new invention will not be successful because electricity costs more than diesel or petrol.   

So it is not true that the car runs on water. It actually runs on electricity which is from coal or diesel or hydro power stations.
 

All energy comes from the sun and energy cannot be destroyed.

All energy comes from the sun which is the main source of energy. Energy cannot be destroyed. It can only be changed into another form.  

When the sun shines on plant leaves which manufacture carbohydrates or starch or sugar by taking the carbon dioxide from the air through a process called photosynthesis. The plant stores the starch in the form of a fruit or cane or in the ground like a potato for men and animals to eat to get energy to do some work.

After millions of years, more and more plants grew and they were compressed to change to coal and petroleum. That is why you can see big coal or diesel power stations that generate electricity for us to use.

Electricity can also come from hydro power station. What is a hydro power station?

The sun energy evaporates the ground surface water which forms into clouds. The clouds turn into rain. All the rain water is eventually flows into the river.

A dam is constructed across a river to dam up the water. When more and more water is dammed up, the water level rises. It is like having something on a table which has kinetic energy. The high water flows down to turn a turbine wheel to generate electricity. That means the kinetic energy has changed to potential energy which can be used to do some work.

Although you may be impressed by this invention that a car can run on water but you must bear in mind that electricity is normally more expensive than diesel or petrol.