Since I’ve been eating and drinking food with mostly real ingredients, I find that if I do try something with processed or artificial ingredients it tastes like crap. Anything with high fructose corn syrup leaves a taste in my mouth. It’s not that I have a bad reaction to any of it, I just find that I don’t like it.
As others have noted, if you’re not used to caffeine and it’s in the sodas, you may react to that. Similarly, you may react to some of the other ingredients, like artificial sweeteners, which some claim can cause migraines, etc. If you’re still consuming other processed food items, you probably won’t notice much.
I found a brand if breakfast cereal that is like the big brands, but uses real sugar and flavors like when I was a kid… my son is amazed at how much better they taste, after being leery because they weren’t the name brand.