There is a kind of Japanese tea called kombucha that contains approximately 0.0065 % alcohol because of the presence of probiotic enzymes that occur as the result of the fermentation process. It can be bought from the store without showing ID, because it hardly contains any alcohol worth mentioning. But I would like to know whether it is permissible to drink it in Islam or not?.
We have read a great deal about the benefits of the tea mentioned in the question; the issue of its benefits should be referred to specialists.
With regard to the amount of alcohol in this tea, it is a very low amount that does not lead to drunkenness, hence drinking it is not haraam because of that.
See the answer to question no. 60212 in which there is an answer concerning fermented tea.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
Everything that is called water is pure and a means of purification, whether some impurity has fallen into it or not, if it is known that it has dissolved into it and disappeared. As for that in which traces of impurity are apparent, it is haraam to use it, because it comes under the heading of using something haraam. End quote.
Majmoo‘ al-Fataawa, 19/236, 237
He also said:
Allah has forbidden impure things (khabaa’ith), namely blood, dead meat, pork and so on. If any of these things fall into water etc and disappear, so there is no blood, dead meat or pork left at all, similar to the case where alcohol disappears in a liquid, then the one who drinks it is not drinking khamr. End quote.
Majmoo‘ al-Fataawa, 21/501, 502
See also the answer to question no. 33763
Based on that, there does not seem to be anything wrong with drinking this tea.
And Allah knows best.