The Messenger of Allah ﷺ prohibited drinking by inverting the heads of skin vessels.

أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ اخْتِنَاثِ الأَسْقِيَةِ

Invert the head of the vessel and he drank from its mouth.

أَنَّ رَسُولَ اللَّهِ ﷺ دَعَا بِإِدَاوَةٍ يَوْمَ أُحُدٍ فَقَالَ اخْنُثْ فَمَ الإِدَاوَةِ ثُمَّ شَرِبَ مِنْ فِيهَا