the real test of anything (including the drinking of water) is whether it has been used with benefit over a long period of time with beneficial and no adverse effects: this is the case with distilled water, which has been used from time immemorial and especially so for fasters since the mid 1800's within Natural Hygiene.
Both of my prolonged fasts were carried out using distilled water, and I am still here in the very best of health 30 years later.
We should also bear in mind that Natures own process within the meteorological cycle produces precipitation which results in distilled water via rain and eventually within fruits and vegetables and other soil grown crops, but the atmospheric and other pollutions of our day will largely make this water impure (unfortunately).
Therefore the only way to secure water that Nature intended, is to mimic its production via distillation.
Truenotes may have a valid point with what is referred to as structured water, but at the end of the day water is H2O (two parts Hydrogen and one part Oxygen) that combine chemically to produce water.