Prestige offers “Pure and Vegetarian” water. Really. The idea proffered is that when you drink regular water, you are ingesting bacteria and viruses, which are “animals.” When you drink chemically purified water, you are ingesting dead-but-formerly-living animals, which is not vegetarian. So you should buy water in which all the dead critters, no matter how small, are filtered out.
Do they believe vegetarians will go for this? The ad campaign ignores the fact that bacteria and viruses are not animals. They have their own kingdoms among living things. Just like plants, which vegetarians eat. It also ignores the fact that we have millions of live bacteria inside our bodies already, helping us to digest food and protecting us from more harmful species.
So yes, it is an advertising gimmick. -via reddit
"For Jains, lacto-vegetarianism represents the minimal obligation: food which contains even small particles of the bodies of dead animals or eggs is absolutely unacceptable."
So yeah, while this appears to be very silly at first, it's really targeting a group of people who do not want to kill anything, even micro organisms for religious reasons.