You can give your hair a great shine and help remove soap build up:

Blondes …. Add a couple of tablespoons of lemon juice to your rinse water.

Brunettes and Redheads … Add a couple of tablespoons of apple cider vinegar to your rinse water.

Stir 1 teaspoon of honey into 4 cups [1 quart]warm water. After shampooing, pour the mixture through you hair. Do not rinse out. Dry as normal.

Source: Fashionpk.net