We would recommend using the Straw Cup for beverages <104 degrees Fahrenheit and non-carbonated drinks only. This is because beverages >104 degrees Fahrenheit and carbonated drinks may cause some liquid to escape from the Upper Straw due to the build-up of air pressure.
This is to ensure the safety of your little ones during feeding as liquids tend to travel faster when warmed and could potentially cause scalding from the hot liquid.