I would suggest starting very slowly with this, since some of the ingredients may upset your child is they are phenol/salicylate sensitive, but honestly there aren't very many juices in it that are super high in phenols/salicylates. This product can turn your childs BMs funny colors, but for the most part it is well tolerated and helps with nutrition quite a bit!
Start with 1/4 teaspoon in a drink three times a day and work your way up to whatever your child can tolerate. I wouldn't go past 2 tablespoons a day for a child under five. It is completely tasteless in such small quantities (that's why you split it up between three drinks instead of having it all in one), but you may want to serve it in a sippy cup that is not see-through. Shake vigorously or it may clog up the spout--but I have never personally had this issue.
Here's another FANTASTIC product you can try:
note: the chocolate version contains a small amount of non-GMO soy
the berry flavor contains NO soy
e-mail the manufacturers to demand a soy-free chocolate version!
This comes in wild berry and chocolate. This product SHOULD give your child trouble if they are sensitive to phenols/salicylates, however my own child is sensitive to apples yet this product gave him no troubles. It may be because the processing of the fruits/veggies lowers the phenol/salicylate count.
My favorite thing to do with this product is to put 1 level scoop into 1 cup of coconut milk yogurt to make chocolate pudding! One serving a day of this awesome product is all you need.
Between the two of them your child will be able to get most of their vegetables--and sneaking in your own homemade veggie/fruit purees can also pick up the slack these products leave behind.
I'm sure everyone has noticed how few fresh veggies/fruits are in the bentos I prepare: this is because mys on simply does not tolerate them. But rest assured, my child still obtains ALL of his daily veggie/fruit servings from other sources!