There's a lot of focus these days on bottle flavoring and carbonating of kombucha. Especially for those interested in home brewing kombucha, the simple reality is that most people got their start in 'buch through trying store-bought kombucha, making this focus understandable.
The issue I'd like to address is the effect RTD (ready-to-drink) kombucha has on home brewing efforts.
Carbonation - Nice, but necessary?
One resounding effect the RTD industry has had on nascent home brewers has been the viewpoint that kombucha is an effervescent beverage. I can't disagree that kombucha is highly desirable and refreshing as an effervescent beverage.
But does it have to be?
The answer is no. Un-carbonated kombucha is just as much kombucha as is carbonated 'buch. Just like un-carbonated water is still water, the carbonated counterpart still tastes fine and is refreshing.
Conversely, think about wine. The majority of wine available is not effervescent at all, but does that mean that champagne isn't wine?
My point is this - as a home brewer, your only responsibility is to yourself, to produce kombucha that you enjoy. To obtain an effervescent kombucha is a fun, often variable process, and a kind of seal of success, but is not necessary. You can flavor kombuchas based on this consideration; one of my favorites is mulled kombucha.
Is it more important to have good flavor or good carbonation?
In home brewing I try to put the greatest emphasis on flavor and let carbonation be a lesser concern, at least for home bottling. People with a keg and CO2 system can achieve carbonation very quickly.
We've all been there before. You are craving a tasty, flavorful kombucha (these are not mutually exclusive) so you head to the RTD aisle at the grocery store. You choose a bottle and go along on your way. Maybe it's too sweet, or perhaps too sour. It might even seem watered down. But hey! It's definitely carbonated.
The flavor should be spot-on, even if the carbonation isn't.
And it's clear enough RTD kombucha has hardly stepped beyond the constant flavor additions that make kombucha taste exactly like this or that fruit, herb or familiar beverage. Not to say these can't be delicious - but I'm pretty sure I know what, say, a beet tastes like, not to mention mangoes, or blueberries, ginger, etc. These are tried and true kombuchas that are classics and will always be delicious. We, as home brewers, can choose to accept or reject that same path and forge into uncharted territory.
What makes 'buch 'buch?
Kombucha is based on tea. Not on fruits, vegetables, spices etc. So why cover up your beautiful kombucha with other stuff that makes it taste like something else? Not that it can't be fun, or that it's not tasty. But we have the opportunity to create something totally unique and special.
Set aside some of your brewing time, vessels, ingredients, etc. to resisting the emulation of any drink you've ever had before. Use the time to explore what makes 'buch interesting, rather than what makes 'buch taste familiar.
Sugar, water, culture, tea, and time.
The most important, simplest way to flavor your kombucha is with tea. It's not an optional ingredient. We'd be ignorant if we said we were familiar with, or even heard of all of the amazing varieties of tea that are available to us.
However, one of the most entertaining aspects of brewing is the use of combinations of herbs and spices, infused and fermented at the same time as the tea.
More thoughts on home brewing
Kombucha has only relatively recently become a retail product, and the real legacy of kombucha still remains inside the home. It's where cultures proliferate and change. They absorb our intent, our energy, our hand-selected ingredients. In home brewing, nothing is lost or forgotten, and everything is exactly as it should be, for better or worse.
Your home-brewed kombucha has a much stronger microbiotic profile and robust nutritional makeup from not having been filtered, piped through machinery, force carbonated and otherwise stabilized to maintain promised shelf-life and alcohol content.
So please, don't feel required to emulate the RTD sector or to assess your own success in comparing your home brew to others'. Look to the tea, coordinate your steep, prioritize flavor, and success will find you.