The Messenger of Allah ﷺ forbade ikhtinath of waterskins. Abu Nadr explained that this means drinking directly from their mouths.
حدثنا يزيد وأبو النضر عن ابن أبي ذئب قال يزيد أخبرنا ابن أبي ذئب عن الزهري عن عبيد الله بن عبد الله بن عتبة
نهى رسول الله ﷺ عن اختناث الأسقية قال أبو النضر أن يشرب من أفواهها
Its isnad is sahih, and Abu Nadr Hashim bin Qasim occurs frequently. The hadith is found in Bukhari 10/89, no. 5625, Fath, in the Book of Drinks, chapter on bending the necks of waterskins, in Muslim 3/1600, no. 2023, in the Book of Drinks, chapter on the etiquette of food and drink, and in Ibn Majah 1/1131, no. 3418.