Hi, B., well I have to say with all of mine as soon as they were introduced to juice the juice went into a sippy cup, as early as 4.5 months, watered down of course. I breastfed all 4 of mine and milk was from me and juice was from the cup. They catch on but you need to establish what comes from where, it might be confusing him if you give him formula in bottle than formula in cup, so give him some water in the cup and maybe stick alittle applesauce on the sippy part to get him warmed up to it. He'll get it. It just takes a little practice, just like using the spoon and fork and chewing. I'll tell ya though, introducing solids was sort of a hit or miss, 2 of mine got it the other two I'd have to wait another month to try again, wasn't the right time. When they were ready they were and thats when they just did it, just like potty training down the road. Good Luck, hth.