i give my 6 month old water. We are trying to figure out how to use a cup, and around here cups are for water. He doesn't drink it, spits most of it back out when he can actually get it in his mouth and not all over the place, but he gets enough fruit so I don't see any reason to give him juice. My older kids all love water, will ask for it over milk or juice, and they won't drink most pops even if allowed. But I have simply always given it to them. If your son is thirsty he'll drink it, if it's all that is there. So keep offering, and don't give in.