Jabir told that the Prophet (ﷺ) went in to visit a man of the Ansar accompanied by one of his companions. He gave a salutation, and the man, who was watering his garden, responded to it. The Prophet (ﷺ) said, “If you have any water which has remained overnight in an old skin we should like it, otherwise we shall sip some from a streamlet.” He told him he had water which had been in old skins overnight, then went to the trellis and poured some water into a jug to which he added some milk which he drew from a domestic sheep, and the Prophet (ﷺ) drank. He repeated this and the man who had accompanied him drank.
Bukhari transmitted it.
Anas said that God's messenger used to breathe three times in the course of a drink.
(Bukhari and Muslim.) In a version Muslim added that he used to say, "It is more thirst-quenching, healthier and more wholesome."
Abu Sa'id al-Khudri said God’s messenger forbade the ikhtibath of water-skins, adding in a version that this means having their heads inverted and then being drunk from.
(Bukhari and Muslim.)