A grapefruit was a citrus fruit native to Earth.
Prior to 2258, Montgomery Scott argued with his instructor over a question of relativistic physics regarding transwarp beaming. The instructor believed that one could only transport an item such as a grapefruit one hundred miles. Scott disagreed, believing that transporting one of these fruits between adjacent planets in the same star system was a cinch, and moreover, he could transport a lifeform just as easily as an inanimate object.
Accordingly, Scott tested his theory on Admiral Archer's beagle, which had yet to reappear by that year. The debacle ultimately ended in Scott's reassignment to the Delta Vega outpost. (Star Trek)
Balok's tranya from "The Corbomite Maneuver" was really grapefruit juice.