Abstract: Described is a reusable thermal insulating container sleeve. The reusable thermal insulating container sleeve is composed of an insulating polymer material and at least one thermally reflective material attached to the insulating polymer material. These materials increase the thermal insulating properties of the sleeve. The materials also prevent the buildup of condensation on the cup which is a common problem among other cup sleeves. The materials are also malleable, durable, and foldable, which permit the sleeve to be reusable. Furthermore, various embodiments of the invention include a sleeve that has a top and/or bottom portion which would cover the bottom of the beverage and further increase the thermal insulating properties of the sleeve. Finally, the present invention includes a method of insulating beverages.