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.
Big batch: To make a batch of 8 cocktails, combine 6 ounces (3/4 cup) EACH of gin, tequila, triple sec, vodka, and white rum in a pitcher. Add 2 ounces (1/4 cup) EACH lemon juice, simple syrup, and cola. Have ice, glassware, and garnishes on hand so guests can help themselves.
Sour Mix: For lemon-lime flavor, replace the lemon juice with sour mix.
More mixers: Try iced tea or Diet coke in place of the cola.
Grateful Dead: Substitute Chambord (black raspberry liqueur) for the triple sec and lemon-lime soda for the cola.
Tokyo Iced Tea: Substitute Midori (Japanese melon liqueur) for the triple sec and lemon-lime soda for the cola.
Long Beach Iced Tea: Substitute cranberry juice for the cola.