Does eating or drinking something forgetfully invalidate the fast?
Eating or drinking something forgetfully does not invalidate the fast. The Prophet Muhammad (saw) said, “If somebody eats or drinks forgetfully then he should complete his fast, for what he has eaten or drunk, has been given to him by Allah.” (Bukhari, Sawm, 26)
A person who eats or drinks forgetfully while fasting should spit that thing and wash his/her mouth immediately, and then continue fasting. If something is swallowed after remembering that one was fasting, it invalidates fasting. (Marghinani, al-Hidayahh, II, 253-254).
Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS,