A water storage unit includes an outer bag with an inlet defined in a top end thereof and an inner bag is received in the outer bag. A coolant bag is received in the inner bag and has coolant received therein. An outlet part is connected to the lower end of the outer bag and connected with a hose so that the user can suck the water in the outer bag. The water is cooled by the coolant in the coolant bag which is located at the lower end of the outer bag. A handle has a clamp slot with which a sealing rod is securely engaged. The inlet of the outer bag can be sealed by the cooperation of the clamp slot of the handle and the sealing rod.