As far as flavored water goes, I have heard that the best way to flavor water is to squeeze a bit of fresh lemon or lime juice into it. Commercially flavored waters often have chemicals in them which may be contrary to a true detox. If you go to a store like Whole foods that does not carry artifical ingredient laden food you are probably more likely to be OK with a flavored water. As far as club soda is concerned, soda of any kind has sodium which we often have too much of already from our past diet and would probably be good to avoid, if you are primrily fasting for wieght loss and less concerned with cleansing I wouldn't think it will inhibit your wieght loss but it may cause you to retain water.