Add the grapefruit juice, sparkling water, lime juice, and honey to a large pitcher. Stir to combine
Fill glasses with ice and pour in the punch. Garnish with lime and grapefruit slice if desired.
Notes
If you want to add tequila to the punch: Either pour 1 1/4 ounces of tequila into each glass before pouring the punch or add 1 1/4 cups of tequila to the pitcher along with the other ingredients.