Try the zarbees cough syrup it contains agave. Currently dealing with croup, and his cough seems to be getting better, but I’ve been doing warm teas with added honey. I also made an at home “cough syrup” where you cut a few slices of onion can be purple or white and add honey too it, let it infuse for a few hours as it releases natural juices and then I just give it to my son in a syringe. I’ve been doing Vicks vapor rub on chest and back and using a humidifier at night and during naps. He still cough but seems to be getting better. Keeping them well hydrated keep the mucous thin and hopefully cough goes away faster that way.
We’ve always used hylands for our toddler and it works so well for her! Zarbees cheats rub is great as well
Seen alot of people making elderberry syrup, marshmellow root and thyme are good too, might be able to find one on the market that has those ingredients
Have you tried a humidifier? I know it’s already really humid but heat and a humidifier seems to help my little one with her coughs (in addition to frequent honey).