I believe that spending money on things that have no nutritive value and are indeed physically detrimental is a sign of either misinformation or addiction, or both.
BAM here it is. Ok, good job picking out all the thing you don't like about soda. Now think of all the things someone might
like about soda. Here's two, for example: they enjoy the taste (probably the big one), or maybe they like the caffeine and don't like coffee or tea. Another: maybe they have soda-drinking friends and it's a social bonding thing.
You value more money and traditional "healthiness" (for this limited case) more highly than the taste or any other factor that might encourage someone to drink soda. That's fine, value whatever you want. But if you begrudge other people their own values, they won't be happy with you. I'm certain there's something you do that someone else on here could say "that thing is categorically bad! and you're addicted so double-bad on you!" Coffee or beer for instance, as you pointed out. Whether you agree that it's true or not, how would that make you feel? I'm going to guess attacked at the worst, if you don't have a logical thought process to back up your actions, or at best mildly annoyed if you've thought it out already and have to explain yourself
yet again to some goon on the internet telling you why your life is wrong.
To encourage discussion, if that's what you want to do rather than just tell people they're wrong, I suggest you ask questions. "Why do you drink soda?" would be a good start. If you understand people rather than talk at them, you stand a better chance of learning something. If persuasion's your thing, you also have a better angle on that since you know where the other person's coming from.
WRT to addiction itself, I'd focus more on values related to the addiction, not the object, in order to discuss pros/cons of addiction. I doubt you'll find many people in the "getting addicted" phase of something who don't enjoy whatever they're doing. Instead, I'd explore (just for example) a freedom angle, where being addicted to something lessens the amount of freedom you have. Just a thought though.
Not a soda drinker, but I have my vices. As do most of us.