I have IC, been water fasting for about a year now, and all I can say is it does not cure it. It does, however, give you the perfect platform to figure out what the triggers are. Avoid anything like Apple cider vinegar, coffee, or other acidic things on a water fast, it’s like 100x worse! I also found out that my bladder likes to make crystals on extended fasts. I don’t know if this is an IC thing, but it might be, so keep that in mind. It DOES clear up your sinuses. After a week you’ll be surprised how much better you feel! Also, weird tip from one IC sufferer to another– glucosamine. It’s weird, but it does work.