It is idiotic to believe all water is equivalent. Indeed, a lot of the marketing around brands is ridiculous but it's not quite the same thing.
I can't remember the name of that portuguese brand of water, 10 years ago, maybe some HNers would know. You would buy it on a hot day on the street, believing it was ice-cold... while its bottle was in fact made of a curious, deceiving translucent material and the liquid not especially cool.