You are very welcome. I have mostly drank filtered water in my numerous fasts. I do not have a distiller either, I live in the US so distilled water is very easily available. Amazon is a good source for pH paper, pH measuring liquid, which is what I used. These are also relatively inexpensive.
Regardless of sun or not, leaving a glass jar with water on the window sill for a day will help. But do drink warm water.
John, if you do not mind what are your goals for fasting? Are you trying to lose weight? Improve your eating habits? Or something else.