Wrap your containers in tinfoil

Try covering your insulated container with tin foil. Foil is a good insulator and will keep the ice cube cooler for longer.

What is the best insulator for ice cubes?

Styrofoam is the best insulator for preventing ice from melting.

How could you insulate an ice cube to keep it from melting?

Wrap a container of ice in a sheet of aluminum foil. Reflective surfaces preserve temperatures at a consistent degree, so the ice melts at a slower rate than ice that is left uncovered or covered in a sheet of a nonreflective material such as paper towels.