reading a few threads about Dr Pepper beer... and trying to brew Mt. Dew successfully... I'm thinking about doing some experimenting myself.
But to avoid issues with preservatives and such, I'm thinking a good way to get the flavor, without the hassle... is just to use these substances AFTER primary fermentation... and maybe after secondary as well.
I'm assuming, because the yeast will be going pretty strong... that adding it WON'T stop the yeast from doing their business, but I guess it's possible.
I'm going to start a batch of cider similar to BrewFrick's PDC, rack in about 7 days... give it another 2 weeks or so... and add Mt. Dew and bottle. This will be in place of the limeade that he suggests later in the thread. I will check on carbonation and cold crash once it's reached an acceptable lvl. How long it takes to carb... and tasting it... will give me a good idea of how much of the sugars in the dew fermented...
I may then try adding the dew upon racking... to give it some time to coagulate and ferment into the overall flavor/color. If that goes well... try adding some to a tea and sugar solution at primary
Depending on how this goes... I may do a Dr Pepper one as well... I'm a Dr Pepper fiend... so that sounds very interesting to me. It'll also be very interesting to see what it does to the overall color.