Slice

To make your own version of the syrup for this orange soda that comes to us from the Pepsi-Cola Company, you need to combine a simple syrup recipe with two popular versions of dry orange mix: Kool-Aid orange unsweetened drink mix and Tang. But unlike the real thing that contains no juice, your homemade version includes a bit of real orange juice solids that come powdered into every scoop of Tang mix. After you make the syrup, be sure to let it cool in the refrigerator before you combine it with cold soda water.  

Source: Top Secret Recipes Sodas, Smoothies, Spirits, & Shakes by Todd Wilbur.