The great debate. I went hunting for this information when my 3yo was downing kombucha and I worried about giving it to her too late in the day. From what I could find, this varies by the length of fermentation and even then--there is debate about whether the yeast need it for food (and therefore digest it--potentially leaving none).
The companies that I could find putting out this information on their kombucha noted caffeine in their kombucha. One company was at 5mg/serving (so almost as low as decaf coffee--which is 3-4) and GT's gave a range of 8-14 mg/serving (hot chocolate is at 14).
Maybe someone can post something more precise than that to help us both!
Heather - Wife , Mommy & Health & Wellness Educator, Speaker & Consultant
Dairy, soy & corn free with limited gluten... yes, really. And journeying towards peace. Blogging about both.
Let me guide you to find the food and lifestyle choices...