I have put hot chocolate into a "polar" water bottle, but it cools down in an hour or so.

I've heard that these 16 oz and 20 oz Stanley thermoses fit well in bottle cages, but I haven't sprung for one yet.

https://www.ghbass.com/product/stanl...0mug%2016oz.do

https://www.ozarksource.com/stanley-...01568-001.html

I think I have this Contigo mug up in Portland. It does fit in the cage well, but I haven't used it that much with the bike. At least I think that is the one as I don't have it with me here
https://www.kohls.com/product/prd-26...ter-bottle.jsp