As Poundstone reports, the basic “cola” formula is very well known. It’s in the Merory Flavoring guides, and lots of independent bottlers have made Cola soft drinks for years. One in my home town used yo, until they closed.
(“Cola” drinks are, as Poundstone points out, a “fantasia” blend – a made-up flavor. Coca Cola originally used it to cover up the bitter flavor of the coca leaves and the Kola nut extract. Kola nut extract tastes nothing like a cola soda, That all "cola: drinks taste basically the same is proof enough that everyone stole from or imitated a common source, probably Asa Candler’s reformulation of Pemberton’s original Coca Cola formula)
The basic of “cola” flavoring are a mixture of vanilla (or vanillin), cinnamon (or cassia), and citrus oil from peels (not citrus juice0. Now that I know that, I can’t help noticing it in each drink of cola soda I take. I also observe that flavored meads containing cinnamon and vanilla taste an awful lot like colas.
The differences are in the proportions and the exact other flavorings used. Coca Cola is thought to have more orange peel oil, Pepsi to have more lemon. you’ll notice that a lot of the “added” flavors both companies have come out with in recent years – vanilla, orange, lemon – simply add on what’s probably in there already. There are rumors of lavender oil, exotic flavors like ylang-ylang, and the like. Again, as Poundstone says, anyone with access to a modern analytical laboratory (with mass spectrometers and gas chromatograph) can quickly enough analyze exactly what’s in either Coke or Pepsi.