Image from mkorcuska.
If you don't eat eggs, or the idea of adding a raw egg to a drink makes you gag, swap in chickpea water (also known as aquafaba) for an egg-less option without losing the frothy texture. Substitute 22mL of chickpea water for a medium egg white in your cocktail recipe, then mix the drink as normal. This switch works best for drinks that are less delicate in flavour, like those with stronger tasting booze or other ingredients like simple syrup or citrus, since the chickpea flavour can come through a bit otherwise.
How to Make Frothy Cocktails Without the Egg [Washington Post]