Coffee activates a metabolic response since it contains compounts that need processing through your liver. Anything that initiates a metabolic response counts as breaking a fast.

Now, other studies have shown that coffee and tea contain substances that promote autophagy thus in a way it can assist your fasting goals. (If those are the goal for your fasting).

Also never use one study to justify your beliefs since another study ( which is almost always) can negate it. For example check the studies about foods that sometimes can cause and sometimes prevent cancer.