I asked Fee Brothers (via their web site) about the sweetness that John found in their bitters and got the following reply:

Hi Chris,

Thank you for reaching out to us!

At Fee Brothers, we use vegetable glycerin instead of alcohol as the base for our bitters recipes. The sweetness your friend noticed likely comes from the glycerin, which naturally has a subtle sweetness. However, it’s not added as a sweetener. Glycerin is commonly used in products for its texture and flavor-preserving qualities.

I hope this answers your question. If you need more information, please reach out to us again.

Thank you for supporting Fee Brothers!

Cheers!

Bernadette
[Bernadette Hayes, qualityassurance@feebrothers.com]