After looking little further my guess is that it is Carissa carandas. Because of the few seeds, the oval leaves and the little latex milk when cutting the fruit.
No, I am living in the Philippines but it does not seem to be a local plant either. I am almost sure now it's the Carissa. It is used in Indonesia to pickle fruit because it has a bit of a bitter sour taste, I tested and it seems. It contains lots of vitamins c. The owner got it from a Chinese, he said you could make wine of it. We took some home first because we thought it was Goci, but it's not.
has thorns, small seeds, oval leaves and has a white sticky fluid when pulled. 
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