An artificial vanilla has been confirmed as an ingredient, as well as lactic acid. I am presently doing an internet search hoping to find info about Dr Pepper's ingredients.
I have lived in the Chicago area and northern Wisconsin. Dr Pepper is available but not like Pepsi and coke.
The straight dope is where I got the info.
Someone wanted a definitive answer about ingredients and prunes. They mentioned the cane sugar as well as information about prunes, vanillin, cherry, cola, and lactic acid which had to be mentioned in Canada when listing ingredients. I will list a hopefully helpful link to Straight Dope's answer.

http://www.straightdope.com/mailbag/mdrpepper.html



I enjoyed your comments. Mark a fellow Pepper

> > > > I *heart* Dr. Pepper. And that makes complete sense for you, being in Dallas. That's where I learned to *heart* it. It's kind of a culture shock to go from Ohio, where DP is a novelty, to Texas, where all the restaurants have Dr. Pepper in their fountains.
> > >
> > > No kidding! I've had such a hard time finding restaurants that serve it outside of Texas. Though I can still find it in a local store...usually. The only exception was when I visited Newport, Rhode Island last summer. I couldn't find Dr. Pepper anywhere in that town.
> > >
> > > Kel"wouldn't you like to be a Pepper too?"ly
> >
> > I think Conroe (or Lufkin?) is the only place where you can get *real* Dr Pepper -- made with pure cane sugar. Oh, it's superb.
> >
> > -Faux "A Texan living in New Jersey" Pas
>
>
> Wow, yep, cane sugar makes any soft drink taste that much better. I would love to try a Dr Pepper sweetened with cane.
>
> So let's see, there's supposed to be 23 different ingredients in the Dr Pepper formula. What do you think they could be? IMHO Dr P has a better flavour than Pepsi, which in turn tastes way better than Coke Classic, which in itself tastes little better than carbolic acid with sugar.
>
> My breakdown for Dr Pepper would be: No prune juice. It doesn't taste anything like that. And maybe the following (I'm guessing here in order of what I think is in it, mind you):
>
> 1) water
> 2) glucose-fructose sugar (cane sugar in Conroe, eh)
> 3) toasted caramel for colour
> 4) syrupy phosphoric acid (that and burnt caramel are main flavour ingredients in Pepper, Pepsi, Coke)
> 5) cherry syrup
> 6) lime, lemon essence
> 7) bubbly carbonated fizz
> 8) who knows... maybe almond extract
> 9) maybe sarsaparilla bark oil from the roots from a birch tree
> 10) salt
>
>
> Hey! with 23 ingredients, do ya think it's possible they might even have PEPPER in Dr Pepper??
>
> Wolfspirit