Its been a while since we got rid of our jujube trees but that doesn't look like one to me. Their leaves are a brighter green in tresses. Hope you have another candidate for your mystery plant:)

Jujubes have parallel leaf veins. Your plant does not. It has features of a Prunus, perhaps Almond. But it has a terrible spider mite infestation. I don't think it's worth saving, whatever it is.

Any idea which plant it is?

As I said, "It has features of a Prunus, perhaps Almond. "