The “forbidden fruit” mentioned in the Book of Genesis is commonly assumed to be an apple, and is often depicted in Western art, but the Bible never identifies what type of fruit it is. The fruit may have been depicted as an apple due to a dual meaning of the Latin word malum, a noun that can mean evil or apple.
Some Slavonic texts state that the “forbidden fruit” was a grape, that was later changed in its nature, much as the serpent was changed by losing its legs and speech. The Zohar (the text of Jewish Kabbalah) also claims the fruit was a grape.
Other Christians sometimes believe that the “forbidden fruit” was the fig, based on the account of Adam and Eve using fig leaves to cover themselves. The fig tree is also the only fruit tree explicitly mentioned in the Genesis 3.
Some Jewish traditions regard the forbidden fruit as wheat : wheat is “khitah” in Hebrew and a pun on khet, meaning “sin”.
As well, many believe the quince tree, native to Southwest Asia, was the forbidden fruit. (Wiki)