What is the ruling on one who drank five minutes after the Fajr adhan, knowing that the Fajr adhan had not been called, then heard the iqamah for prayer and completed the fast?

Whoever eats or drinks, thinking that dawn has not broken, but then it becomes clear that it has, must make up that day if their fast was obligatory. This is the view of the majority of scholars, including the Four Imams, based on the Almighty's saying: "Then complete the fast until the night." [Quran 2:187] Such a person did not complete their fast; rather, they ate during the day.