I'm not including diet soda as different products use different kinds of fake sugar and ingredients. Just the HFCS colas. Why do you drink that much diet soda btw? Seems like a weird addiction.
Because I like it and I have never developed a taste for coffee so it serves as my primary caffeine source. I don't really consider it to be an addiction aside from the caffeine which I'll 100% admit to.
I'm fairly confident I'd be able to tell regular Pepsi & Coke apart even without consuming them regularly. Pepsi is notably sweeter. Any more than a couple oz of either one though is disgusting. I'll use real Coke as a mixer but that's about the only time I encounter it.
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