Fill a highball glass with ice. Add the gin, tequila, triple sec, vodka, white rum, lemon juice, and simple syrup.
Using a bar spoon, gently stir. Top with cola. Garnish with lemon slice and serve.
Notes
Tequila: Choose tequila blanco, aka silver tequila, which has not been aged. This lighter tequila is great for mixed drinks.
Triple sec: Or substitute another orange liqueur such as Cointreau or Grand Marnier.
Simple syrup: To make it yourself, combine 1 cup water and 1 cup sugar in a small saucepan over medium heat. Stir until sugar is dissolved (do not boil). Remove from heat and cool before adding to your cocktail shaker with the other ingredients. Store leftover simple syrup covered in the refrigerator for 3-4 weeks.
Yield: This recipe makes 1 cocktail.
Glassware: Long Island Iced Tea is traditionally made in a highball glass, an 8-ounce to 12-ounce glass tumbler such as a Collins glass.