Practicing (ie. trying to the improve skill of) fasting. I have the best results when I start after lunch and drink bone-broth on the fasting days; I treat it like a improvable skill, not as an exercise in sheer willpower; fwiw my record is 15-days.
You're question is kinda rules-lawyery. It would break a water fast. Joe Cross fasted for 60 days on vegetable juice and made a movie about it; he lost 100 pounds, but yes its not a water fast, but that's somewhat the point of my comment, that there's more to fasting than simply not eating.
