Hey guys, anything that goes through the liver ends a fast. This includes coffee and obviously anything with calories, but also things like apple cider vinegar and sweeteners.
That being said, ending a fast with something that keeps insulin suppressed (eg. Healthy fasts) still replicates SOME of the benefits of fasting. But mostly depends on your level of blood ketones which are really behind the therapeutic potential of fasting and ketosis - ESPECIALLY FOR BRAIN HEALTH.
Since in the brain they are anti inflammatory, reduce reactive oxygen species, and improve redox potential among other things.
Cheers,
Chett