I tried a home remedy that worked better than any cough syrup I've ever had : one quarter teaspoon of cayenne pepper , one quarter teaspoon of ground ginger , 1 tablespoon of honey , 1 tablespoon of Apple Cider vinegar , and 2 tablespoons of water. Mix it all up in a bottle or something and take a teaspoon every 6 hours or so and your cough will be gone. I always double the portions and pour them into an old cough syrup bottle and keep it in the refrigerator. I kid you not, this works better than ANY cough syrup I've ever had. Try it! It's way cheaper too.
As a long-time voice student, I suggest drinking Black Licorice Tea. It tastes awful (unless you like black licorice). Walgreens sells a "mucus relief" product (their brand) that works well. You can also "sniff" warm water with a little salt to clean your sinuses, blowing your nose after each dose...1-2x. DO NOT take decongestants as, over time, you can dry out the throat tissue to a point of losing your voice PERMANENTLY.