Watch out for store-bought Kombucha...they don't let it ferment long enough (because some idiot sued them over 0.5% alcohol content). Because it doesn't ferment long enough, it's too sugary. You might think you're drinking something "good" when it's simply sweet tea with carbonation.
#3. We toss out any kombucha older than 3 or 4 days.
I could be mis-reading your post or mis-understanding what you're describing, so take this advice with a grain of salt.
Kombucha's health benefits only show up 2-3 weeks (depending upon the temperature/season) after a "fresh batch". You want it to be vinegary, because that means that the fermenting process is complete, and you have all kinds of B vitamins and other good stuff.
When you want to drink the vinegary stuff, you take 1/4 or 1/2 cup and then water it down with fruit juice/water/etc. This way, you get the health benefits + good taste.
- Many people will do a secondary ferment, where they make this mixture and then bottle it and put it in the fridge for another 1-2 days.
- Cooling it down and adding fruit juice will add carbonation and it will taste great.
- That's what most companies "used to" do. (But due to the lawsuit, the amount of true, vinegary mix they put into the store bottles is so small that it's mostly just a sugar drink.
If you're drinking "young" kombucha that isn't very vinegary, you're basically drinking sweet tea. You're not getting the full health benefits.