Laura,
There are lots of fruit juices but they usually have some suagr added. Look out for the ones that say 100% juice if you don't want him to have sugar. Most places only serve ice that has been made from botteld water, they get big bags of ice in and they are safe for your drinks. Tap water isn't really suitable for drinking, I lived in Turkey and I never drank it although I know people who did and they were ok, I certainly wouldn't recommend it while you are on holiday though.
Toasted Mallow,
Wine is quite expensive in Turkey, you can expect to pay about £10 a bottle in a restaurant. I like Kavak, it is a white wine, fairly dry. Cankaya, Doluca, Kavaklidere are all quite nice but really Turkish wine is not so good. Tureky ahs got more expensive but it will still be cheaper than Greece, Spain or France. If you eat at local kind of restaurants rather than the toursity ones you will get a much nicer meal and it will be much cheaper, although you may not always be able to get wine with your dinner there.