At home I would call it a thermos flask or vacuum flask. At work in the chemistry laboratory, I would call it a Dewar.

I call it a "thermos" or just a "flask". Sometimes I say "vacuum flask", but not often. I have said "hot water bottle", but a hot water bottle is... not really the same thing. It might be something unique to my family. I have not heard of a "Dewar bottle" or "Dewar flask".

Thermos or vacuum flask. Never heard of the others.

vacuum flask!