We really do not want to tell you what it tastes like, but it is neutral and not flat. Tasting water is difficult and depends on a number of things – eg. best temperature for tasting water is 7C. Your mood is important. How thirsty you are is important. What you just ate is imprtant. Your personal taste and liking is perhaps the most important parameter.
Changing the taste is easy: Find the salt, mineral, aeration, carbon filter, fruit or vegetable you want to add to the water, and then enjoy.