Shama-il Tirmidhi Chapter 31, Hadith Number 5 (201).

Sayyidina Anas ibn Malik radiyallahu anhu relates that Rasoolullah sallallahu alaihe wasallam drank water in three breaths (i.e. in three gulps/sips) and used to say, It is more pleasing and satisfying in this manner.

It has been prohibited to drink water in one gulp. The Ulama have written many harmful effects in drinking water in one breath. It especially weakens the muscles and nerves. It is also detrimental for the liver and stomach.