What is the primary juice used in a Greyhound cocktail?

The Greyhound cocktail is primarily composed of grapefruit juice, which gives the drink its distinctive tart and refreshing flavor. This cocktail is typically made with vodka and grapefruit juice, highlighting the bright and slightly bitter notes of the grapefruit. The choice of grapefruit juice as the main ingredient not only defines the cocktail but also contributes to its reputation as a refreshing option, especially popular in warmer weather. By focusing on grapefruit juice, bartenders can create a drink that balances the sweetness of the vodka with the tangy acidity of the juice, making it a classic choice in cocktail culture.