Anas (may Allah be pleased with him) reported: “The Messenger of Allah (peace be upon him) used to breathe three times in the course of a drink (he used to drink in three gulps).” [Al Muslim, Book #023, Hadith #5029]
Commentary from Riyadh as Saliheen: “Water should be drunk in three breaths, that is one should breathe three times outside the drinking vessel one is drinking from. This habit has a salutary impact one one’s character and helps one avoid doing things in haste.”
Ibn Abbas (may Allah be pleased with him) reported that the Messenger of Allah (peace be upon him) said: “Do not drink in one gulp like a camel, but in two or three (gulps). Mention the Name of Allah (i.e. say Bismillah) when you start drinking and praise Him (i.e. say alhamdolillah) after you have finished (drinking).” [at-Tirmidhi]
Commentary: This hadith too, prohibits us from drinking water in a single breath. It is preferable to say Bismillah everytime we drink and alhamdolillah everytime we stop drinking.