From Sahih Bukhari (Hadith 1637):
Narrated Ibn `Abbas:I gave Zamzam water to Allah's Messenger (ﷺ) and he drank it while standing. `Asim (a sub-narrator) said that `Ikrima took the oath that on that day the Prophet (ﷺ) had not been standing but riding a camel
Reference: Bukhari 1637