
Grapefruit vodka is a flavoured vodka: a neutral base vodka given a predominant grapefruit flavour beyond that of its raw materials.
Clean and light-bodied on the palate, finishing on a tart, faintly bitter grapefruit note; the aroma is pronounced and citrus-forward, the base spirit itself contributing no distinctive character.
Bartenders pour it as the base measure, stirred or shaken, where it sets both the alcohol backbone and the drink's dominant grapefruit aroma. Because sweetening varies from dry to noticeably sugared between bottles, the balance a given bottle contributes cannot be assumed and may need adjusting.
Rebuild it on a plain full-strength vodka by adding a real grapefruit source — fresh fruit, juice or a grapefruit flavouring — since the class is just a neutral base plus grapefruit; a plain or differently-flavoured vodka alone fails, supplying the neutral strength but none of the defining grapefruit aroma.
Grapefruit liqueur
Grapefruit vodka is a high-strength flavoured spirit (EU min 37.5% ABV; US min 30%) with limited sweetening, whereas a grapefruit liqueur is a lower-strength, heavily sweetened product.
A neutral, near-colourless base vodka distilled to high strength carries little character of its own; grapefruit flavouring, with or without added sugar, is added afterward. Under US rules the base must meet the standard of identity for vodka before the natural flavours go in. Bottlings range from essentially dry to noticeably sweetened, since sugar may be added.