Allah's Messenger (ﷺ) forbade the bending of the mouths of water skins for the sake of drinking from them.
Sahih al-Bukhari Book 74, Hadith 51
← Previous Hadith Allah's Messenger (ﷺ) said, "Extinguish the lamps when you go to bed; close your doors; tie the mouths of your water skins, and cover the food and drinks." I think he added, ". . . even with a stick you place across the container."

Sahih al-Bukhari Book 74, Hadith 50 Next Hadith → I heard Allah's Messenger (ﷺ) forbidding the drinking of water by bending the mouths of water skins, i.e., drinking from the mouths directly.

Sahih al-Bukhari Book 74, Hadith 52