You can drink too much water, but it takes quite a lot.
I would take a look at the artificial flavors, sweetening and coloring and other ingredients in them. They may be the culprit.
I'm not a big plain water drinker either, but found that things like Crystal light, there is something in that stuff, that I can tolerate a bit of, but can't overdo.
For water, I toss a couple of lemon wedges in with the water in a big ole bottle, a bit of flavor, and for me much more thirst quenching.
Just my 2 cents.