Insulated cups are the best at keeping water cold. They feature a double-walled design with an insulating layer between the walls, which prevents heat from transferring from the outside of the cup to the water inside. Some insulated cups also include a copper lining, which helps conduct heat away and keeps water even colder.
Popular types of insulated cups include:
* Stainless steel cups – durable and available in many styles.
* Plastic cups – lighter and less expensive, though less durable.
* Ceramic cups – good for home or office use.
* Glass cups – stylish but less effective at insulation.
Regardless of material, choose a cup with a tight-fitting lid to retain cold temperatures. Adding ice cubes can also help keep water colder for longer.