I gave my son honey, that is what zarbees consists of mostly. Not sure it helps but he likes it. Pediatrician also gave us inhaler with some medicine to use when he is coughing a lot and that really helps! When he gets sick my son coughs as well, dry air from heating and cold outside does not help, even though we use humidifier.
I have zarbees and hyland and honestly it did nothing for my 20 month old. I do give him zyrtec which has helped tremendously. We found out he is allergic to oak trees and oak tree pollen so he was always congested when he spent time outside with his daycare ( oak tree heaven where we live lol) he's doesn't get a cough or cold much since we found out the solution. He does get ear infections a lot but that's due to his allergies. If we forget to give him zyrtec every single day he will end up with an ear infection 🙃. I suggest getting your little one tested for allergies!
Haven't given zarbees yet. When my 21 month has a cough I just use a humidifier in his room and before bed I give him some zyrtec or flonase (bc it helps with congestion) and i give him a small spoon of honey before bed. It seems to help