For winter camping I use a Nalgene bottle full of boiling water, which I toss into my sleeping bag to pre warm it.
Before sleeping I pull it out and give it to the dog who knows to curl around it.
Before sleeping I pull it out and give it to the dog who knows to curl around it.
Can leave it in the bag all night, it'll still be warm in the morning.
Inside a snow cave he’s OK.
I’ve been given bottles made from other plastics but I’ve always been dubious about them.
I have cracked the lids, but that takes a lot of work and an aged lid. The lids are made of a different, softer material which is more compliant to make a good seal. I do replace the lids every few years.
Speaking of getting your gear soaked (not): a good habit in the snow is to put a nalgene of water upside down into the leg of each boot overnight to keep them from freezing. I guess you’d be concerned about that too.