Iced-coffee base, coaster or sleeve?
Separate support, condensation and temperature.
A coaster
A coaster may address the furniture surface. It does not confirm the cup fits Steadi, and stacked layers can affect support.
An insulated cup
Temperature control is a drinkware feature. Check that container’s actual base and any boot rather than assuming an insulated cup is compatible.
A wider base
Steadi supplies a resting footprint for compatible containers. Use a dry supported spot and clean any moisture as needed.