Fruit, water, and yogurt. I have never had a constipation problem with my daughter, but she wanted to eat apples when she was 4 months old because she sees us eating apples almost every day. I grate apples in her cereal, but now at 2 she can easily chew soft ones (golden delicious). I ripen pears until they can be almost pureed (4-5 days after they are purchased from the store) and they are so sweet that my daughter literally cries if I don't give her another one. Yogurt has natural bacteria that aid digestion, you can even try plain yogurt not the sweet one, you may be surprised. If she nees to be on soy, there are many soy yogurts out there, too. Where I live we have a good selection of tropical fruit - papaya and mango are her favorite. There is a lot of soft fresh fruit that kids would eat because it is very sweet. I think we tend to underestimate what they would like based on what we like, for example I really don't like papaya, although I know it is good for you, including for digestion.