Grapefruit juice is the juice extracted from white or Ruby Red grapefruits. It can be freshly squeezed from the fruit or is available already squeezed in bottles or as frozen concentrate.
To juice a grapefruit:
Cut the fruit in half crosswise and use a handheld or electric juicer to squeeze the juice from each half. For clearer, pulp-free juice, or to remove seeds, pour the juice through a sieve.