杯 pairs wood 木 with 不 for sound — the earliest Chinese cups were carved from wood (and lacquered beautifully). The material changed to porcelain and glass; the wooden radical stayed as a fossil of the first cups.
杯 measures drinks: 一杯水 (a cup of water), 一杯茶 (a cup of tea — with 茶 you learned), 干杯 ('dry the cup' — cheers!). At a Chinese banquet 干杯 taken literally means bottoms-up, so pace yourself. The World Cup is 世界杯 — the same humble cup, scaled to planetary size.
Wood 木 that is NOT 不 a tree anymore — carved into a CUP.
干杯 'dry the cup' is cognate in spirit with Japanese kanpai and Korean geonbae — same characters, same toast, three languages.