N.H.
Hi J.! You shouldn't even be thinking about whole milk for at least 3 or 4 more months. My son's doctor said that until they reach about 12-14 months they really need to be on formula or breast milk for development.
As far as sippy cups, we went from water to juice mixed with water and he did fine. We never did formula in a sippy cup. We always fed him by bottle and let him snck with sippy cups.
Good luck!