2 ounces tequila (recommended: El Tesoro)
2 ounces freshly squeezed grapefruit juice
1/2-ounce freshly squeezed lime juice
Splash lemon-lime soda (recommended: Sprite or 7-Up)
Combine all ingredients in a cocktail shaker with ice and shake well. Serve over the rocks in a Collins glass.
This is my favorite summer drink.