Yes i completely agree with Archus. If we include Coconut water this would no longer constitute a water-only fast. The fact that it contains calories is the greatest reason, but a water-only fast is also disrupted, interfered with, and broken by the addition of vitamins, minerals, teas or anything else.
Distilled water is far and away the best way to go since aside from being extremely pure, it is free of inorganic minerals, minerals which our body can not utilize and are thus treated as waste products. Distilled is the water best able to carry toxins out of our body including these inorganic minerals found in non-distilled water.