If a person is having Suhūr and the Athān is called. Is it obligatory upon him to spit out what is in his mouth or should he eat it?

Shaykh Muqbil ibn Hādi al-Wadiʿī:

That which is in his mouth then he should not spit it out, but nothing should be eaten that isn’t in his mouth after [the athān].

Except for water, for it has been reported in the Sunan of Abū Dāwūd by way of Abū, Hurayrah that the Messenger of Allāh ﷺ said: “If one of you hears the call (to prayer) and the vessel is still in his hand, let him not put it down until he fulfilled his needs with it.” So there is no problem in drinking if the Muathin has called the Athān with the condition that the water [utensil] is in his hand.