My wife brews kombucha and she has tried adding blueberries and mangos when she bottles in grolsch swing-tops. sometimes she will add a little fruit juice instead of whole fruit. We have tried pomegranate and blueberry/cranberry combos on the juices. They turn out great!
When you add fruit at bottling it will carb up. We have not gotten this down to an exact science regarding C02 volumes. I have been concerned for bottle bombs because her bottled kombucha is heavily carbed after a week sitting at room temp. Thus, I suggested she use the swingtop bottles, I hear they are stronger than regular beer bottles.