You should always drink when you are thirsty – never a certain amount. Different bodies need different amounts of water. Let your body tell you. Drinking too much water can actually cause dehydration because your body will purge the excess. Water does not cause fat loss.  The best water to drink is purified or filtered.  Sodas contain high amounts of sodium and do not actually hydrate your body.  Stay away from sodas, and drink purified water when you are thirsty.  Eating plenty of fresh fruits and vegetables will also maintain proper hydration levels and help you metabolize more fat.