This right here, I do the same and have ice cold water all day. I have a few Nalgene bottles too, the trick is to fill them up to about half an inch where the neck starts. This is the only way I have busted a Nalgene bottle, by over filling it and freezing it solid. I had one Nalgene bottle that lasted ten years, I froze it solid five days a week. I also buy Powerade in powder form, its a lot cheaper mixing it. I go through about two gallons of water a day.Fill up 32 oz bottles of empty Gatorade bottles with water and freeze them. Put them in your cooler with ice, helps keep the ice from melting.