I’m not sure whether this video is true or not because it was done without showing who is the demonstrator. Meaning, it might be a fake demonstration. Peoples can create any video as they like as long as it looks real to people who watch it.
The video that you will see here is about a demonstration to make a water burn. The trick is done by using two batteries and sink them in a cup of water for 30 minutes. Then take out the batteries and light the water with fire. And the water is really burn!
After I watched the video, my assumption is, the batteries react with the water and release chemical reaction and produce ions. These ions is flamable and thats why the water is burning when lit up with fire. But, can we drink the water? I guess not.