What is the best cough medicine?

Hydration/Expectoran: Best cough medicine is to treat the cause of the cough like allergies/asthma/pnumonia/copd/stop smoking if smoker and hydration by drinking more fluids which makes the secretions thin and easy to cough out expectorations with or without cough suppressant like dextromethorphen and rarely opiates there is not one cough medicine for every one.It depends if cough is dry or with expectoration ask md.