The Millionaire No. 1 is a vintage cocktail that was created in the 1800s and was first published in The Savoy Cocktail Book by Harry Craddock in the 1930s. It's traditionally made with dark rum, apricot brandy, citrus, and sloe gin, a British liqueur made with gin and sloes, which is a fruit similar to a plum.
Add rum, sloe gin, apricot brandy, lime juice, and grenadine to a shaker.
Fill shaker with cubed ice.
Shake for 10-20 seconds.
Using a Hawthorne and fine mesh strainer, strain into a sour glass.