Honestly, I hate juices, but I love tapioca/sagu. You just have to make your own mix of fruit juice and enjoy.
I never use refined sugar, but you already know that. A little bit of coconut sugar worked fine (you can use maple syrup also).
2-4 cups fresh juice (if using bitter fruits, use 2 cups)
3 cups water
1 cup sagu
Coconut sugar, to taste
Cinnamon, to taste (optional)
Boil water. When boiling, pour sagu. Mix and let it simmer. When the sagu pearls seem to be a little transparent, add juice. If you want, add cinnamon now. When the pearls are totally transparent, turn off the heat and add sugar. Done.