In its basic form, the classic Daiquiri is just rum, lime juice and a little sugar. The second most popular version is to add a small splash of maraschino liqueur. For a variation, I like to add a small splash of Cointreau or other orange liqueur instead.

You can use either simple syrup or confectioner's sugar to sweeten this drink. Avoid regular granulated sugar, as it doesn't dissolve well in cold liquids.