Distilled spring water is fine, because this has removed the inorganic minerals that would only have served to clog the body as waste.
Only organic minerals have benefit to the body as found in plant-foods, which have metamorphosed the minerals into an organic form that makes them bioavailable and nutritious for the human body.
It is a fallacy that distilled water leeches minerals from the body except for those that are inorganic; it does not leech organic minerals that have become a part of the cell structure.
The bad breath you have experienced while fasting is due to a toxemic body, where the lungs act as one of the organs of elimination. When toxemia is lowered or eliminated altogether via water-only-fasting, the breath becomes sweet and clean.
It is also a common experience in those who fast, and who do not suffer from toxemia, (retained toxins) not to experience any bad breath at all, but remains sweet and clean from the outset.