A milkshake insert is a STRAW that is used to stir and mix the ingredients of a milkshake. It is usually made of plastic or metal and has a handle on one end for easy gripping. The STRAW is inserted into the milkshake and then twisted around to mix the ingredients together. This helps to create a smooth, creamy texture. Milkshake inserts are also known as milkshake mixers and are commonly used in restaurants and cafes.