Kombucha, kefir, kvass and fruit ferments share a mechanism and almost nothing else. A plain comparison of what each is made from, what ferments it, how it tastes, and how much alcohol it carries.
A bottle of milk kefir, a jar of kombucha and a glass of dark kvass can stand side by side on the same shelf and share almost nothing but the word on the label. One is milk thickened and soured by a cluster of rubbery grains. One is sweetened tea colonised by a flat beige disc. One is grain or bread steeped in water. Different vessels, different timescales, different cultures doing the work — and different amounts of alcohol at the end.
Fermented drinks are a family, not a single category, and the differences between the branches are larger than most shelf labels suggest. What follows is a plain survey of the main ones. None of them is a version of another, and the differences are worth having in front of you before you choose.
The four questions worth asking about any fermented drink
Almost every useful distinction between fermented drinks comes down to four things. Once you know them, an unfamiliar bottle stops being mysterious.
- Base ingredient — what is being fermented: tea, milk, sugar water, grain, fruit, vegetables.
- Culture type — what does the fermenting: yeasts, lactic acid bacteria, acetic acid bacteria, Bacillus species, or a mixed community of several at once.
- Typical flavour — sour, sweet, malty, sharp, savoury, or a combination, and whether it carries carbonation.
- Typical alcohol level — a by-product of some ferments and negligible in others, depending on which organisms are present and how long they work.
Kombucha: sweetened tea and a SCOBY
Kombucha starts as brewed tea with sugar dissolved into it. The culture is a SCOBY — a symbiotic culture of bacteria and yeast, which forms the familiar pale disc that floats on the surface. The yeasts convert sugar into carbon dioxide and ethanol; acetic acid bacteria then convert much of that ethanol into acids, which is where kombucha's sharpness comes from.
The result is tart and lightly effervescent, with a vinegary edge that grows more pronounced the longer it ferments. Flavour varies enormously with tea type, sugar quantity, ambient temperature and time — a two-week summer batch and a two-week winter batch are not the same drink. Much commercial kombucha is filtered, and a second fermentation with fruit or juice is a common way to build carbonation.
Water kefir and milk kefir: two drinks, one word
These share a name and very little else. Water kefir, sometimes called tibicos, ferments sugar water — often with dried fruit, a slice of citrus or a little molasses — using translucent grains that look like small crystals. The grains are a matrix of polysaccharide housing lactic acid bacteria and yeasts. The finished drink is light, dry, faintly sweet and briskly fizzy. It is closer in body to a soft drink than to anything dairy.
Milk kefir uses a different culture entirely: soft, cauliflower-like grains bound together by kefiran, a polysaccharide the bacteria themselves produce. These ferment lactose in milk, thickening it and turning it sour. The taste is tangy and slightly yeasty, thinner than yoghurt and more effervescent. Both kinds of grain reproduce as they work, which is why kefir grains tend to be passed hand to hand between households rather than bought.
Kvass-style grain and beetroot ferments
Kvass belongs to a long domestic tradition across the Baltics, Poland, Ukraine and Central Europe. The classic version ferments stale rye or dark bread in water, usually with a little sugar and sometimes raisins, driven by a mixed population of wild yeasts and lactic acid bacteria. It comes out dark, malty and bread-like, mildly sour, with a soft natural fizz — savoury where kombucha is sharp.
There is a second branch that skips grain altogether: beetroot kvass, made by submerging raw beetroot in salted water and letting lactic acid bacteria work. That version is earthy and saline rather than malty, and is used in cooking as often as it is drunk.
Fruit and herb ferments
The broadest and least standardised family. Here the base is fruit purée, juice or whole fruit, frequently with herbs, roots or spices alongside, and the culture varies more than in any other category — wild populations from the fruit skins in some traditions, deliberately added cultures in others. Tepache, made from pineapple and its rind, sits here. So do the many household ferments built on seasonal fruit and honey.
Because the base is fruit rather than tea or milk, flavour follows the season and the harvest rather than a fixed recipe. A cherry ferment and a watermelon ferment made in the same vessel by the same method taste nothing alike, and neither is a version of the other.
Boza, kanji, amazake and ginger beer
Boza, from the Balkans and Türkiye, ferments millet, maize or wheat into a thick, pale, spoonable drink. Kanji, from northern India, ferments black carrots with mustard seed into something sour and deeply savoury. Amazake, from Japan, uses koji mould on rice and finishes sweet rather than sour. Traditional ginger beer relies on a 'ginger bug', a wild starter of ginger, sugar and water. Each answers the four questions differently.
How much alcohol is in fermented drinks?
This is the question that most often goes unanswered on labels, and the honest reply is that it depends on which organisms are present and how long they are given. Where yeasts convert sugar, ethanol appears as a by-product. Where the ferment is led by bacteria producing acids, far less of it does.
Broad, approximate patterns — not fixed values, since time, temperature and sugar all move the figure:
- Kombucha — commercial batches are typically held low, often around 0.5% ABV or below; home batches left longer or kept warmer can run noticeably higher.
- Water kefir — usually low, but rises with a long ferment or a generous amount of sugar.
- Milk kefir — generally low; traditional extended ferments produce more than shop-bought versions.
- Kvass — traditionally a low-alcohol drink rather than a zero-alcohol one, with home versions varying widely.
- Traditional ginger beer — can exceed the others comfortably, which is why commercial ginger beer is usually a soft drink made by a different route.
One anchor is useful here. Under EU food information rules, a beverage containing more than 1.2% alcohol by volume must declare its actual alcoholic strength on the label. Below that threshold the picture is less uniform: what may be described as 'alcohol-free' or 'non-alcoholic' is set nationally and differs between member states. If a drink's alcohol content matters to you, the label and the producer are the only reliable sources — category alone will not tell you.
These are not competing versions of one drink. They are different foods that happen to share a mechanism.
Where ETRAFLORA sits in this landscape
Our drinks belong to the fruit and herb branch. The base is ionised, highly alkaline water at pH 9.2, combined with seasonal fruit and vegetable purées and juices, herbs, artichoke syrup, honey and stevia. The ferment is led by Bacillus subtilis alongside other live cultures, rather than by a SCOBY or by kefir grains — a different culture type from any of the families above. Fermentation happens under pressure, in a closed vessel, held below 45 °C for the whole cycle, in small batches made by hand; the detail of that method is set out on our production page. A minimal quantity of alcohol occurs naturally, as it does in any live ferment; it sits below the 1.2% by volume at which a strength must be declared, which is why the drinks are sold as non-alcoholic.
In flavour terms the range sits closer to fruit ferments than to malty or dairy ones. Tarhun is a tarragon ferment, fresh and lightly sweet with a gentle sparkle. Anti Beer leans the other way, built around hop character. Seasonal releases follow whatever the harvest gives — cherry in its season, watermelon in another. The full range is in the drinks catalogue, shipped chilled across the EU.
Choosing between them
Choose on taste and on what you want the drink to do at the table, not on hierarchy. If you want something sharp and vinegary to cut through rich food, kombucha does that. If you want body and tang, milk kefir. If you want something malty and savoury, a kvass-style ferment. If you want fruit and herb character with fizz, the fruit ferments. And if you are making your own, start with whichever base you already keep in the house — the culture is easier to find than the habit.