If the fasting person rinses out his mouth or cleans his nose with water and some of the water enters his throat unintentionally, does this nullify his fast?
If the fasting person rinses out his mouth or cleans his nose with water and the water enter his inner body, this does not break his fast, because he did not do that intentionally. This is due to Allah’s Statement: But what your hearts purposefully intended. 
1. Al-Ahzab 33:5
Shaykh Muhammad bin Saalih al-`Uthaymeen
Fatawa Islamiyah Page no.260 Vol: 2