N Acetyl Cysteine - It is a precursor of glutathione, and is commonly thought to be useful both for thinning mucus and against inflammation. You can read about it here:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6458826/
https://bronchiectasisnewstoday.com/2019/05/09/n-acetylcysteine-potentially-beneficial-bronchiectasis-patients/

There are also numerous discussions about it in this group. If you go to the main MAC & Bronchiectasis group page and put NAC in the search box for Search this Group, you will find many discussions and posts.

I was a little hesitant at first, but tried it to clamp down on exacerbations. In the past 2 years, I have only had two - only one of which required treatment. Previously, I had 4-5 episodes a year.
Sue