The most revered Prophet (SAW) used to sit down while drinking water. Prophet (SAW) also used to breathe three times in the course of drink.
Anas (RA) reported: “The Messenger of Allah (SAW) used to breathe three times in the course of a drink (he used to drink in three gulps).” [Al Bukhari & Muslim]
Ibn Abbas (RA) reported that the Messenger of Allah (SAW) said: “Do not drink in one gulp like a camel, but in two or three (gulps). Say Bismillah when you start drinking and Alhamdulillaah after you have finished.” [Al-Tirmidhi]
The Messenger of Allah (SAW) also prohibited us from breathing in the drinking vessel because the bad smell or spittle may flow into the drink. This is both vile as well as injurious to one›s health. Abu Qataadah (RA) reported, “The Prophet forbade breathing into the vessel while drinking.”
If a person drinks in one gulp, he would most probably breathe into the container and that is forbidden.
Medical experts say it is beneficial to drink water while sitting down. Drinking water while standing hits the lower part of the oesophagus strongly and this leads to a dilation and relaxation of the sphincter that connects the oesophagus and stomach, which finally leads to a medical condition called Gastro Oesophageal Reflux Disease called GERD in which the acids in the stomach pass backward through the “relaxed” sphincter and start “burning” the acid-intolerant oesophagus.
The Ayurvedic way recommends drinking in small sips. It also urges the person to sit down. It says: “Take sips, not full-glass chugs. Small sip, swallow, breathe. Repeat.”
The zam zam water, however, has to be drunk while standing and facing the Kabbah. Ibn Abbas (RA) reported: I served zam zam to Allah’s Messenger (SAW) and he drank it while standing. Al Muslim [Book 023, Hadith 5023]
Ibn Abbas reported that Allah’s Messenger (SAW) drank (water) from zam zam in a bucket while he was standing. Al Muslim [Book 023, Hadith 5024]
Ibn Abbas (RA) said: “If you drink zam zam water, drink your fill, turn toward the Qiblah, say “Bismillaah” and breath three times and when you finish, you should say “Alhamdulillaah.” -Al-Haakim
There are ulema who allow drinking water while standing. They also quote Hadiths to prove their point. However, it seems the emphasis is on drinking water while sitting. The Muslims, therefore, need to act accordingly.