What is the ruling for one who forgot and drank water while fasting on the Day of Ashura?

The ruling for someone who eats or drinks forgetfully while fasting is that they should complete their fast, and there is no sin upon them, and their fast is valid. This is based on the saying of the Prophet, peace and blessings be upon him: "Whoever forgets while he is fasting and eats or drinks, let him complete his fast, for it was Allah who fed him and gave him drink."