When you begin drinking water with vitamins, flavors and other additives then you are no longer just drinking just water, but now are consuming chemicals that someone has placed into their product. Many of these additives such as basic minerals are fine, while the debate on how beneficial they are is a totally different matter. Some waters however, add sugar or artificial sweeteners which must be considered health wise.
Again, the human body needs water, and whether it is from the tap, a Dasani type bottled, or an effervescent product like Pellegrino, the benefit to the body is the same. In fact, the water benefit of a Cola is equal to these water products, just with the downsides of colors, flavor and sugar.
The takeaway here is that all water is the best! Question courtesy of Mario Uriate!