How we eat fruits in Viet Nam?

I wonder who was the inventor of those magical mixture of ingredients for eating fruits!
Not every fruits! But many!

I remember my student time! Sitting with some friends from Cuba in the train on the way back to our city, after one month working in the farm, we talked about many things, just to kill time and we ate green apple. With salt mixed with sugar !?

Cuban seemed surprised and asked why salt & sugar? I said "for better taste!"

              Ready-to-eat mango Keo stall near to Ben Thanh market. 
                 Do you notice two big pots of salt & chili and chili saté on the right hand side? 

That's true!  But I can't remember why salt & sugar. Usually no sugar!!!

Anyway it reminds me how we eat some fruits, even sweet but especially green, sour ones in Vietnam we always need special dips!