What happens to sugar during kombucha fermentation
Sugar is the part of kombucha that people ask about most, and it is the part most often misunderstood. It appears on our ingredients list, right there after the tea, and that surprises anyone expecting a drink with so little sweetness to have left it out altogether.
It has not been left out. It has been eaten.
Why is there sugar in kombucha at all?
Because the culture has to eat something. Kombucha starts life as sweetened tea, and the sugar is not there for your benefit. It is food for the SCOBY, the symbiotic culture of bacteria and yeast that does the actual work of turning tea into kombucha.
Take the sugar away and nothing happens. You are left with cold tea. There is no version of this drink that skips the step, which is why you will find sugar on the label of every genuine kombucha on the shelf, ours included. We use organic cane sugar, and our ingredients list says plainly what becomes of it: cane sugar (transformed during fermentation).
What does the culture actually do with it?
It breaks it down. Over the course of the ferment, the culture works through the sugar in the tea and converts it into the acids that give kombucha its character. That gentle sourness, the tang underneath the fruit, the thing that makes it taste like kombucha rather than iced tea: all of it comes from sugar that is no longer sugar.
This is the same transformation that happens in sourdough, in yoghurt, in a good vinegar. Something sweet goes in, time passes, and what comes out is sharper and more interesting than what you started with. Fermentation is not an additive process. It is a conversion.
How much sugar is left in the bottle?
Per 100ml, our kombucha contains 2.9g of sugar and 11kcal. That is what survives the ferment, and it is the number printed on every bottle.
There are no sweeteners or sugar substitutes going in at the end to round off the edges. What you taste is the tea, the ferment, and the organic flavouring, and nothing is doing any quiet work in the background to make it more palatable.
Does a longer ferment mean less sugar?
Broadly, yes. The longer the culture has at the tea, the more sugar it gets through and the sharper the result. That is the lever every brewer is pulling, and it is a balance rather than a race. Ferment too briefly and you have sweet tea with a hint of sourness. Ferment too long and you have something closer to vinegar than a drink.
Where you stop is a decision about flavour, and ours is made batch by batch in Glasgow rather than by a timer. We ferment on French oak, which is unusual for kombucha and is a large part of why ours tastes rounder than most. Once a batch is where we want it, the ferment is finished and the drink is bottled. What is in the bottle is what we signed off.
Why we do not use sweeteners
It would be easy to. Ferment hard, strip the sugar right down, then add something back to make it drinkable. Plenty of drinks are built exactly that way.
We would rather solve it with better ingredients. Whole leaf organic Assam rather than the dust and fannings that go into most tea-based drinks, French oak for depth, and small batches we can actually taste before they go anywhere. Our drinks are raw and unpasteurised, never heat treated, because the gentler route keeps the flavour the ferment built. That is also why we are certified organic by the Soil Association.
So is kombucha a sugary drink?
It is a fermented one, and that is the more useful way to think about it. The sugar on the label is the starting point of the process, not a measure of what ends up in the glass. If the ingredients list made it clearer, it would read something like "sugar, mostly gone".
If you want to taste the difference the ferment makes, the Original is the one to start with. It is the least dressed up of our flavours, which makes the tea and the oak easiest to pick out. It was also chosen as a BBC Good Food Best Kombucha, 2026.
Build your own case of 12 from any of our five kombucha flavours, or read more about what makes kombucha raw and why it matters.