I agree with the other respondents here ... coke or pepsi or 7-up will tend to feed the pathogens you are trying to eliminate. Also, because of the highly acidic nature of those sodas, your Miracle-Mineral-Supplement will go after those substances first. So, you will lessen the effectiveness of your Miracle-Mineral-Supplement , and you will also heighten your potential for nausea due to the reaction.
I know that for me personally, most of my worst reactions (stomach-wise) to Miracle-Mineral-Supplement have been after eating or drinking acidic food or drink (ie. a chocolate croissant, etc...)
You will still get benefit from MMS with a little bit of soda added, I think, but with the aforementioned caveats.