ENOfficial
‘Amr b. Shu'aib, on his father’s authority, said his grandfather told that he saw God’s messenger drink both standing and sitting. Tirmidhi transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ عَمْرِو بْنِ شُعَيْبٍ عَنْ أَبِيهِ عَنْ جده قَالَ: رَأَيْت رَسُول لله صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَشْرَبُ قَائِمًا وَقَاعِدًا. رَوَاهُ التِّرْمِذِيّ
sunnah.com