I had a look and this might be a completely ignorant suggestion (I don’t have a dog) but to me it was very surprising that dogs would like frozen food, so maybe you should explain that/why they do. Just seemed counterintuitive, I’ve never seen anybody give anything frozen to their dog.
Ice cream style treats (made for dogs, so not real ice cream) have become very popular with dog owners. You'll see them carried in all major grocery stores in the US now.
A lot of dogs (mine included) love to crunch on ice cubes. You can also find a lot of recipes for frozen treats online - I started by looking there first, but they were all heavy on ingredients my dog isn't fond of (he really just likes meat).
Might be a geographical/climate thing. I'm in San Diego, so frozen treats are good year round here.