From the Super Mario Wiki
Artwork of a Papaya

A Papaya is a kind of fruit found in Isle Delfino, and on Earth in the tropical regions of the Americas. It appears in the game Super Mario Sunshine. It is a fruit that Yoshi can eat. When Yoshi eats the fruit, he becomes orange. He can spit orange-colored Juice, and it has various effects on enemies.

In the Super Mario World episode King Scoopa Koopa, papaya fries were served at Koopa's fast food stand.