Is it permissible to drink kefir, knowing that it contains a very small amount of alcohol and is made from milk with properties similar to yogurt?

It has not been reported that kefir was a gift from the Seal of the Prophets to a non-Muslim king. If yeast and kefir are intoxicating, then they are unlawful, according to the Prophet, peace and blessings be upon him: "Every intoxicant is khamr (definition), and every khamr is unlawful." If they are not intoxicating, then there is no harm in them as long as they do not cause damage. If they do cause damage, their use is prohibited, according to the Prophet, peace and blessings be upon him: "There shall be no harm or reciprocating harm."