I think mydreamcametrue used to add coconut milk and rice protein to it.
I don't add anything to it. At Bella's age, Riley was still nursing some, and when he switched fully to Rice Milk, at around 15 months ?? I was told by my paed that he should drink about 16-18 ounces of it a day. As it doesn't have a lot of calories in it, I didn't stress about trying to make him drink more than that, but tried to get more calorific foods into his diet instead, such as avocado etc. He is also okay with yoghurt, so he has at least 8oz of yoghurt every day.