Hop off the ferry from Xiamen when you disembark at Gulianyu, and not too far ahead you'll see a McDonald's to the left. Veer right for local options like this wood apple, also called rose apple or wax apple (Y1 each). I had planned to wash them with some bottled water back at my hotel — streetside fruits and vegetables can be dodgy in China — but managed to leave my bag behind at a later stop, before I'd had a taste. I came across them again, in a larger, duskier guise, only when I reached Taipei, across the Formosa strait.
Fruit and Vegetable Vendors
Longtou Lu, Gulian Yu, Xiamen