Oh, so kind of like a mocktail?
I made a pretty good one at Sizzler once. I can't remember the exact ingredients, but I remember using 1 part coca-cola and 1 part creaming soda as a base. However, this is made from soft drinks, obviously.
Also, words of warning: Coconut milk does not taste good when mixed with anything carbonated.
Cranberry juice makes a good extra.
Apple juice makes a good base.
Juice from berries tends to be quite sour, so it should be put with sweet juices like mango.
Where I live, chirimuya (or however it is spelled in english), is fairly common and it is served as a desert with chilled orange juice. In a small bowl, it is filled with orange juice and added like a quarter of fruit.
If you can put that on a blender and make it liquid, it would be very tasty and refreshing (must be served chilled).