I never understood why people were so obsessed with canteen cups.

I drink water right out of my water container (usually it would be a 2 liter pop bottle) and if I need to heat something I have a small pot or mess kit for that.

I can't say what I would do these days exactly because I have not been hiking in a while, but I usually had a plastic insulated mug with me for hot drinks. If I go to the trouble to heat water to make hot coffee, I want it to stay warm until I am done drinking it.