I keep a couple of 2-liter soft drink bottles filled with salt water and frozen in my deep freezer at all times and toss them in a cooler if we are going grocery shopping and might not be back home directly. When I used to be into cycling and would do long rides, I would use a 2-liter bottle frozen for my water bottle. By the time I was ready for my first drink, enough of it had melted. I could always add a bit more water to it from any faucets along the way and still have ice cold water for quite awhile.