Ziziphus species?- Singapore market

Plant ID 100513ASP10 : Attachments (1).  2 posts by 2 authors.
This fruit was taken in a Singapore market in October 2012. It is said to be edible, eaten raw, cooked or pickled.
Details of the tree is not known.
Can you please ID this
Zyziphus ??
I think this is Manilkara zapota (sapodilla)
Seems too small for Manilkara zapota
Also looks dry, Zizyphus seems likely choice.