A cocktail shaker is a device used to mix drinks with shaking. When you put ice in the shaker, it quickly cools the beverage before serving. This is all to do with mixology. We make one flavorsome drink, by mixing different spirits, juices, herbs, and other ingredients together and harmonizing the different elements into. This is the best reason to buy a cocktail shaker.
The secondary benefit of using a cocktail shaker is to dilute the water. The amount of time that a drink interacts with ice during the shake is enough to add the water to the mix. It gives a smoother finished cocktail.