How To Make A Homemade Thermos?

You can use materials that insulate heat:
Styrofoam
fiber glass
paper
wood
duct tape
corrugated cardboard
down feathers
wool
cotton
bubble wrap
calcium carbonate
newspaper
tin foil
air
polystyrene cup
oven mitts
socks
foam
blankets
sawdust
...

You can put tin foil on the outside of a water bottle then put bubble wrap un top of the tin foil then a gaterade bottle on top then put felt on top of the gaterade bottle for design