What is the purpose of adding a splash of soda in a Mind Eraser?

The purpose of adding a splash of soda in a Mind Eraser is primarily to ensure easy drinking through a straw. This cocktail is typically served with a generous amount of ice and is meant to be sipped through a straw, allowing the drinker to mix the layers of liquor and soda as they consume it. The soda not only provides carbonation but also helps to dilute the stronger spirits, making it easier to enjoy the drink without overwhelming flavors.

While carbonation is indeed one of the attributes provided by soda, the main focus in the context of a Mind Eraser is the practicality of drinking it through a straw rather than just for the presence of bubbles or flavor enhancement. This makes it more accessible and enjoyable, especially considering the typically potent ingredients used in the cocktail.