My son coughs a lot. Probably his respiratory system is sensitive.
When he starts to cough at night, it drags on an on and he has trouble keep sleeping.
I came up with a simple solution.
Wet a towel (but not too much), and place it on the bed head. Add some water in his old baby bathtub and place it near the bed.
It seems like the towel hanging above him is close enough to give enough moisture to soothe coughs.
It doesn't require humidifier or electricity. No medicine if the coughing is not too bad and not accompanied by other symptoms.
It works great.