A Sharp is a type of apple that is relatively high in acidity but low in tannins and sugars – the fruit will taste sharp (acidic) but not astringent (bitter). Many cooking apples fit this profile. Eating a Sharp apple is like sucking on a slice of lemon. The Granny Smith is America’s best known sharp apple, Heirloom varieties such as the Rhode Island Greening are gaining popularity amongst cider makers seeking sharp apples.