No we would not advise putting Chilly's Bottles in the freezer. The reason is that this will have no effect on the Chilly's Bottle due to the double wall vacuum insulation. This technology means the Chilly's Bottle is not affected by the outside temperature so the freezer will not be able to cool the water inside the Chilly's Bottle. It has also been known to crack Chilly's Bottles and break the vacuum seal if left in the freezer.
For best results for cold water, we recommend using very cold water from the fridge or tap and filling your Chilly's Bottle with ice cubes