I usually just use whatever fruits I have on hand - usually some overly ripe bananas, plus some pineapple, and maybe some leftover coconut milk, if I have some, or a few drops of coconut flavor. If it is excessively sweet (bananas get that way!), I put some unsweetened yogurt in it. I blend it on low speed, in the Vitamix, then add some chia seeds, and let them gel for several minutes. Then I blend it on high, until the chia seeds are not really visible. Then I pour some into a container, to refrigerate, for later (or a friend visiting!), then drop a bunch of ice into the VM, and blend on high (maybe adding more ice), until ice is totally ground up. This is a frequent desert, in the summertime, using the refrigerated extra for a later smoothie or two. I can't think of the last time I had to add any sweetener.