It depends what type of fasting you’re doing if you’re doing an absolute fast or a dry fast then yes Espresso will break your fast. If you’re partaking in intermittent or water fasting water is allowed and so are zero calorie liquids.
And here’s the good news
Espresso has ZERO calories! as long as it’s free from milk and sugar that is, and as a bonus, the caffeine will aid fat loss.
So if your fasting technique allows water go ahead and treat yourself to a few Espressos.