Before i start im going to say this.
Water isn't supposed to have a taste. For all of you saying you like the 'taste' of water, what your tasting is all the chemicals and other assorted goodies that are either added after purification or are only able to be purified down to 'safe' levels. That, and it might taste like copper or whatever your water pipes are made of.
That said, coke is popular because of two things. One is advertisement. Two is that sugar, like alchol and nicotine, is addictive.
Diet isn't much better though. For most cokes the sugar replacement is a antidepressant. That and its roumored to cause bone weakening in young children. Some of them use Aspartame which is made up of, essentially, poisons.
Also, Touko, I don't know what can of coke you are looking at but i think that the regular can of coke has something like 37 grams of sugar, not 400.