To the OP:
There are ways of creating your own tinctures/extracts with everyday ingredients but they require a good deal of work and time.
For Instance:
If you want a more authentic orange flavoring (or any citrus) you can do something similar to the following by extracting the essential oils and leaving the sugars behind:
3 x Orange (Make sure it is a kind you will because your going to have to eat it)
1 x Clear Sterilized Glass Container able to be sealed (enough to hold 20ml to 30ml)
Cheese Cloth
Zesting Tool or Fine Grater
PG or VG (for tincture) I prefer VG
Grain Alcohol can be used as a distilling agent but it can become an assault on the taste buds if the proof isn't high enough. Adding about 10% alcohol to this recipe can improve the leeching abilities of the mixture.
1. Zest your Oranges
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&sqi=2&ved=0CDYQtwIwAw&url=http%3A%2F%2Fwww.ehow.com%2Fvideo_4790427_make-orange-zest.html&ei=6yhFT_HJIYmCtgfEzsz9Ag&usg=AFQjCNFOpaqErbQRQqKmLGf_ShlOoV4jIw&sig2=U_tRYbFd0HQErVj5AiR1iw 2. Transfer the Zest to the glass container
3. Add ~20ml of distilling liquid.. (VG in my case)
4. fold the cheese cloth into a square so that it is wide enough to cover the mouth of the container but still about 3 layers thick
5. Screw on lid and place in a nice and sunny spot for around 2-4 weeks depending on temperature and desired concentration.
6. Eat your oranges this will give something to do while you wait. You don't want to waste them do you?
6. After the tincture has had enough time to cure you can remove the cap and use the cheesecloth to strain out the zest material while pouring into a sterilized container.
7. Using a new piece of cheese cloth repeat the straining process a couple of times until there are no more zest particulates left.
8. use your new orange tincture to add a natural orange flavor to your mix.
Unfortunately as I've never given it much thought I don't know how you could achieve a similar result for Cola but this may be worth looking into. I know you can easily make a root beer using distilled water and some high proof grain alcohol along with fresh sassafras root from your backyard. Sassafras tonics and liniments used to be big medicine in the Ozarks back in the day, my parents taught me how to make sarsaparilla when I was a kid.
Best Regards,
Canniscam