The best replacement for kombucha is kefir.

The best alternatives to kombucha are rated as following:
★★★★★  kefir
★★  apple cider vinegar
★★  kevita
★★  water kefir
★★  jun
★  kvass
★  rejuvelac
★  milk kefir
★  chaga
★  sauerkraut
★  acv
★  synergy
★  kimchi
  apple cider
  coconut kefir

Your alternative for kombucha is not listed? Suggest!
Speaking about kombucha, one probably shouldn't forget about scoby.

Other search terms related to kombucha and their ratings are:
★★★★★ scoby
You have in mind a companion for kombucha and it is not yet here? Propose!



Google Trends

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kombucha
kefir
apple cider vinegar