Rinsing the nose and mouth when fasting
It is proven that the Messenger of Allaah (peace and blessings of Allaah be upon him) said to al-Laqeet ibn Saburah: “Do wudoo’ well and make the water go between your fingers, and be thorough in rinsing the nose, unless you are fasting.” So he (peace and blessings of Allaah be upon him) told him to do wudoo’ well then he said: “…and be thorough in rinsing the nose, unless you are fasting.” This indicates that the fasting person may rinse his mouth and nose, but he should not be too thorough in doing so lest the water reach his throat. As for rinsing the nose and mouth, they are essential when doing wudoo’ and ghusl, because they are obligatory parts of those actions, whether one is fasting or not. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him)