Kombucha tea is a fermented drink made with tea, sugar, bacteria and yeast. Although it's sometimes referred to as kombucha mushroom tea, kombucha is not a mushroom — it's a colony of bacteria and yeast.Kombucha tea is made by adding the colony to sugar and tea, and allowing the mix to ferment.The resulting liquid contains vinegar, B vitamins and a number of other chemical compounds.lthough it's sometimes referred to as kombucha mushroom tea, kombucha is not a mushroom — it's a colony of bacteria and yeast. Kombucha tea is made by adding the colony to sugar and tea, and allowing the mix to ferment. The resulting liquid contains vinegar, B vitamins and a number of other chemical compounds.