Is it permissible to stop eating and drinking at 1:08 AM, knowing that the Shar’i Fajr (dawn) time begins then, while the sun rises at 4:50 AM?

One must abstain from all things that break the fast upon the rise of true dawn and continue fasting until sunset, for Allah the Almighty says: (And eat and drink until the white thread of dawn becomes distinct to you from the black thread [of night]. Then complete the fast until the night.) So, whoever drinks at the time of the Fajr adhan (definition), and the adhan was called after dawn broke, must make up that day. There is no harm in delaying the Fajr prayer until fifty minutes before sunrise, because its time extends from the rise of dawn until sunrise.