One of the earliest reasons for the connection between tea and Buddhism was highly practical.
After Buddhism spread through China, monks often spent long periods sitting in meditation, reciting sutras, and maintaining demanding daily routines. One of the most basic challenges of prolonged meditation was simple: sleepiness.
Tea happened to be especially well suited to this way of life. It helped promote alertness, did not cloud the mind in the way alcohol could, supported long periods of seated meditation and chanting, and had a light, restrained character that fit naturally with the relatively simple lifestyle of Buddhist monasteries.
From around the Wei, Jin, and Northern and Southern Dynasties onward, tea gradually became more common in monastic life. By the Tang dynasty, drinking tea in Buddhist monasteries had become widespread.
This practicality is one of the central reasons tea and Buddhism became so closely connected. The relationship did not begin because tea was inherently mystical. Rather, tea was physically and mentally compatible with the demands of Buddhist practice.
Since Buddhist discipline traditionally prohibits intoxicating alcohol, tea also became an especially suitable alternative.