How can I prove it?

[Ikku]

I think that ginger ale at the coffee shop is just Coke and Sprite mixed together.

[wgToonces]

Get a job there and see for yourself, or pay someone who works there a heafty fee for them to tell you their secrets.

[Bubbles]

or buy a ginger ale, then mix coke and sprite a bunch of times until you get the same mixture

[andriaSRH]

Take a sample of the "ginger ale" to a scientist.

[Weedguru_Fire_Inside]

I'd agree with andria on that, as impractical as it may be. It's the only way you'll acquire certainty.

[Bubbles]

isnt the only real difference in sprite/coke the color/taste?

cause i mean its probably hard to tell the difference between phosphoric acid in a can of coke and a can of sprite.