Rice Dream Enriched (has the same vitamins as milk) milk. Their dairy-like treats are great too. If you want to add calories to the Rice Dream you can add a little bit of walnut oil/canola oil to it or even a little coconut milk and their are also Rice Protein powders which can add more protein (though our son hated the powder).
I wouldn't use a ton of soy as this can cause issues in CFer's as well. We strive for a nice blend of some soy products and just great foods - something like 2 slices of soy cheese, 2-3 glasses of Enriched Rice milk, a bit of soy sour cream with veggies, and the rest comes from foods rich in calories and not high in any oils that cause inflammation. From 1year to 18 months, we felt it was important to help him drink less of his calories (at that time breastmilk) and start trying to go for 5-6 small meals a day with no drinking in between. I gradually started nursing him after a meal instead of before and only offering sippy cups of Rice milk after he ate. This seemed to pack on the pounds and helped keep his appetite strong before meals.
Our son still can't eat dairy...it just does a number on his tummy and butt. Again, I think variety of foods and shifting thinking away from the drinks being a primary source of calories is helpful. As he get a little older you can have fun with power smoothies.
Best of luck...Jody
Some web sites for Dairy Free stuff:
https://www.cherrybrookkitchen.com/items.asp
<a target=_blank class=ftalternatingbarlinklarge href="http://www.livingnaturally.com/common/recipes/recipes_results.asp?id=237&storeID=WJU4DJ2CQFSR2L1C0G03N0ET9DG2FLQ7
">http://www.livingnaturally.com...R2L1C0G03N0ET9DG2FLQ7
</a><a target=_blank class=ftalternatingbarlinklarge href="http://www.purelydecadent.com/products/coupontwodollar_y.html
">http://www.purelydecadent.com/...oupontwodollar_y.html
</a><a target=_blank class=ftalternatingbarlinklarge href="http://www.tastethedream.com/products/rice_dream.php
">http://www.tastethedream.com/products/rice_dream.php
</a><a target=_blank class=ftalternatingbarlinklarge href="http://www.chreese.com/products.itml
">http://www.chreese.com/products.itml
</a>
There is also a good book called Allergy Free Cooking for Kids by Savill.