Well, plain tap water is.. meh.
But if you spoil your taste with soda, juices, and basicly only drink flavoured stuff water may be a bit too difficult to handle.
Putting all those sugars and chemicals in your mouth when your thirsty isnt realy that good for you. What helps is putting a bit of that lemon juice concentrate in your glass of water, just a little bit. Like a teaspoon or so. Not that great for the teeth overall, but not as bad as drinking soda instead.