What is the problem with using a flavored kombucha as a starter? In all the videos I see about starting to make Kombucha, they all seem to say (roughly) "You want to use 'original' Kombucha, and not flavored. If you use the flavored stuff, you are going to have problems." But I cannot find anywhere an explanation of what these problems are. I get the feeling that people just repeat what they have heard and don't even know why they are saying it beyond that.

For additional context: I made a scoby from a 1.4L bottle (the huge one) of GT's Trilogy Kombucha. They don't call it flavored, but it is red instead of... yellow/tan(?). I'm wondering what kind of problems I should be looking for.

On the left is the one that everyone says to use. On the right is the one I used.
There's two reasons for preferring the original instead of the Synergy version:


Most people make kombucha with a neutral base and then put in additional flavors when bottling. By starting with a pre-flavored kombucha, it gives you less flexibility in the flavors you might chose for yourself. For example, if you wanted to make a strawberry &amp; basil kombucha, that might not want the raspberry and ginger in the Synergy bottle you selected.
The original version, since it's 100% kombucha instead of having other juices in it, gives you the best chance of forming your own mother as quick as possible. The Synergy should still work, but may take longer to generate a useful mother.


In any case, the Synergy bottle should still work, and after a few batches I doubt there will be much residual effects from the juices in it. It's just that using the original will give you a neutral kombucha base faster than the other bottle.