Try wrapping them with foam, or rap them with towels and tape the towel onto it

All I did when it got below freezing was to have 3 sets of water bottles for each cage.

When I went out, I'd take fresh bottles with tepid water, and switch out the bottles. Take the frozen ones inside to thaw.

How cold it got determined how many times I'd have to switch the bottles. If it wasn't much below freezing, just switch once in the morning because the bottles wouldn't freeze during the day (my rabbits had shelter)

If it got down to 50 below, every couple of hours. It wouldn't take the bottles long to freeze, but if the rabbits got all they wanted to drink at least every other hour, they were getting enough.

You an also put heat lamps near the hutch and if they are close to the water bottles, the water won't freeze.

Mine would get fresh water several times a day plus I kept a container with snow in it in their cages. That way they always had something. And they do eat a lot of snow. Even if there was water available.