This is probably a good idea, and I hope it catches on. We tax cigarettes heavily because it is non-smokers who end up footing the bill when smokers head to the hospital, and because cigarettes harm the people around the smokers as well.
The same is true of bottled water. Those who choose to drink endless bottles of water are greedily consuming their fellow citizens oil supply (because the plastics take oil and also because companies ship these bottles of water all over the country). Moreover, they are contributing to the production of billions of plastics bottles that will essentially last forever and pollute our already over-polluted planet.
So, as long as we're going to tax someone, lets tax the a-holes.
The topic of bottled water is a favorite of mine. There's nothing wrong with tap water people - you have been tricked by PepsiCo yet again.