Skip the sippy and just go with a cup. He's old enough. When you feed him solids, put a little bit of water or breastmilk/formula in a small cup (the best are the ones with handles, so he can start helping soon). Put the cup to his lips and tip it up. For now, it' going to be mostly on him rather than in him. I even would spoon the milk from the cup to my baby's mouth and then move the cup closer. Do just little bits at a time till he's used to it, then gradually give him more. He's going to want to hold the cup and wave it around - let him play with it when he's empty so he can figure it all out.
We did this with all 3 kids. The oldest was a bottle baby and the other 2 were exclusively breastfed (never took a bottle). They were all drinking well from a cup by a year. (In fact, it was nice when I wanted to go for a few hours that the younger ones would drink milk from a cup enough to hold them till I cae home).
It's true that they can't carry the cup around the way they can a sippy. But it's better for them to get in the habit of drinking at the table or highchair. Carrying around a beverage and sipping at it all day can add extra calories, reduce appetite for other foods, and contribute to cavities. It's also not a great habit to be in, and you don't want to have to wean him from it, besides from the breat or bottle.