Haha yeah the coffee is weird topic...it depends which reasons are you doing the fast for...It doesn't break a fast from the metabolical perspective. It has zero calories soo your body doesn't experience any insulin spike etc and still stays in ketosis. Body is still "eating" own weak cells and basically making your immune system stronger etc etc...clensing and detox would be better without coffee but if you're fasting to rebuild immune system, coffee should not have an effect..at least that's what internet says :DD