If you try to log food while fasting, KAI will ask what you'd like to do:
"You're currently fasting"
End fast — Stops your fast and opens food logging
Continue to food logging — Keeps your fast running and opens food logging (useful for logging coffee, water, or small items that don't break your fast)
Cancel — Returns to the Daily Log without logging
Choose the option that fits your fasting approach. Some people allow certain items during a fast; others prefer to end the fast before eating anything.