Drinking from a water skin by turning the mouth is not allowed

Narrated Abu Sa'id Al-Khudri (may Allah be pleased with him): The Messenger of Allah (peace and blessings of Allah be upon him) forbade turning the water-skin upside down (i.e., the Messenger of Allah, peace be upon him, forbade drinking water from the mouth of the water-skin by turning it over).

Abu Huraira (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings of Allah be upon him) forbade drinking from the mouth (opening) of a water-skin or water-bag (the narrator is unsure), and also forbade that anyone should prevent his neighbor from driving a peg into his wall.