Which of the two holes in the coffee cup is for drinking? The big hole in the coffee cup cover is used for drinking coffee, while the small hole is used for ventilation. When drinking coffee, if the mouth wraps the bottle mouth completely, the bottle will gradually shrink with the speed of drinking coffee, and this small hole is an air inlet designed to prevent negative pressure from forming in the cup, which can release the pressure. In addition, the two holes of some coffee cups may be about the same size. If this happens, you don't have to be too rigid about which is the drinking hole and which is the exhaust hole, just suit yourself.