Not all soft drinks contain caffeine. 7-Up, for example, does not; Jolt Cola contains the maximum amount permitted by the FDA.
Although not a recipe for Shasta sodas (there are many flavours), here is a link to an article where some enterprising Brits seek to re-create the Coca-Cola flavour and include ingredients and techniques. It's interesting that they use a little alcohol (vodka) in the recipe. http://www.guardian.co.uk/lifeandstyle/2006/jul/28/foodanddrink.shopping Hoyt,VA