Eating and drinking forgetfully does not break the fast. The Prophet said, "If somebody eats or drinks forgetfully, he should complete his fast because Allah has made him eat and drink.” (Bukhari, Fasting, 26; Muslim, Fasting, 17). A person who eats and drinks forgetfully should bring out what is inside his mouths and wash his mouths when he remembers he is fasting and he should complete his fast. The fast of the person who continues eating and drinking after remembering he is fasting is invalidated.