杯杯 is the reduplicated form of the measure word 杯 (bēi, 'cup'). In Chinese, reduplicating a classifier gives it the meaning of 'every' or 'each' — so 杯杯 means 'every cup (of something)', focusing on each individual unit. You'll see it in expressions like 杯杯茶 (every cup of tea) or 杯杯咖啡 (every cup of coffee). It is not used with numbers; instead, it substitutes for a specific quantity, emphasizing each one.