Vanilla eXee
Wouldn't drinking only RO water leave you deficient? It's one of the processes we use in salt water aquariums that basically removes EVERYTHING including the minerals that living things need. The salt mixes then re-add the necessary ones as well as salt. Doesn't sound like a good plan for living.
As for vitamin water, there's no reason not to get one every once in a while. I only drink water, tea, and coffee, but every now and then I will have a soda, like for a special occasion or if I'm sad and I want to treat myself. I do love root beer, though I prefer water or tea over everything. I've actually never heard of that.
I always figured they added minerals to it "Just cause".
So I guess tap filters would be the best choice, even though they don't remove fluoride.
In one particular: Glaceau Vitamin Water:
Vapor distilled water, crystalline fructose, citric acid, caffeine, ascorbic acid (vitamin C), gum Arabic, natural flavor, electrolytes (calcium, magnesium, and potassium), gum ester, zinc picolinate, vitamin E acetate, vitamin A palmitate, niacin (B3), pantothenic acid (B5), beta carotene, Siberian ginseng and guarana extracts, cyanocobalamin (B12), caramel color, pyridoxine hydrochloride (B6)