Abstract: Disclosed are exemplary embodiments of adapters for beverage container thermal insulators or drink holders. In exemplary embodiments, the adapters may be used for adapting beverage container thermal insulators or drink holders that are pre-sized for standard sized 12-ounce cans for use with bottles (e.g., standard sized 12-ounce longneck bottles, etc.) and other can sizes (e.g., “16-ounce tallboy” cans, “12-ounce slim” cans, etc.). In exemplary embodiments, the adapter may be made (e.g., injection molded, etc.) from one or more thermally-insulative materials for covering and thermally insulating the upper portion of a bottle or can that would otherwise extend outwardly above the beverage container thermal insulator or drink holder. By thermally insulating the portion that would otherwise be exposed, the adapter can significantly reduce the rate at which the beverage within the bottle or can will warm up, e.g., when placed in the sun, etc.