Coffee has no calories in it so doesn’t break a fast. Interestingly it could actually benefit it. A 2014 study showed coffee induces autophagy in mice which is the mechanism causing the main health benefits of fasting. They point to polyphenols in coffee 'promoting health by stimulating autophagy' concluding 'both natural and decaffeinated coffee similarly induce a broad organism-wide autophagic response'. At Exhale we love nothing more than a delicious cup of our high-polyphenol decaf before bed to make us benefit even more from our overnight fast.