https://abukhadeejah.com/sahur-in-ramadan-if-you-hear-the-adhan-for-fajr-and-you-have-food-in-your-mouth-or-a-glass-of-water-in-your-hand/
Sahūr in Ramadān: If you hear the Adhān for Fajr and you have food in your mouth or a glass of water in your hand? ―Shaikh Muqbil Ibn Hādi Al-Wādi'ī