'Amr bin Shu'aib on the authority of his father and grandfather reported:
that they saw Messenger of Allah (ﷺ) drink standing, and sitting.[At-Tirmidhi].The last three Ahadith point out the permissibility of eating and drinking while walking or standing or sitting, but drinking in the sitting position remains the best.
App reference: Book 3, Hadith 43
Arabic/English book reference: Book 3, Hadith 770