My preference for soy milk is a brand called SILK, and instead of plain old Soy Milk we use their Vanilla flavored Soy Milk for our smoothies. At our house we have many berries growing wild all over the place, and we collect these blackberries well into August and freeze them. These make a great base for a Soy Milk based smoothie. We also use frozen mixed fruit with berries that we find at the grocery store. Even though it is not hand picked and frozen on site, these bags of fruits are still a good source of fruit to use for the base of your Soy Milk Smoothies.