Lightly crush blueberries with a fork to release juice
Add crushed blueberries and lavender to the bottle
Fill with kombucha leaving 2–3cm headspace
Seal firmly and store at 21–27°C
Check carbonation daily from day 2 by opening a crack over the sink
Refrigerate once carbonated (strong hiss when opened)
Open cold over the sink and strain through fine mesh before pouring