Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said that ablution after eating, and cupping for the fasting person, were mentioned in his presence, and he said: Ablution is only due to what comes out, not what goes in; and the fast is broken only by what goes in, not by what comes out. And the Prophet (peace and blessings be upon him) said: "And sniff water deep into the nose, unless you are fasting."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8253