In my travels I had the chance to test some different kinds of fruits, one that I loved (and never had to buy, because I found loads of ripe fruits lying on the ground, nobody seemed really to care about them) is JUJUBE, in north Thailand, but you can also find in China, Africa... They are light brown, 1-2 cm in diameter, quite sweet with a bit of sour (but not a lot), and you can stuff your pockets with and snack on them... tasty, in my opinion. Another small fruit that is really sour (and sweet) is tamarind, I really enjoy small amounts of it... the small size of these fruits is practical, you eat them like nuts or berries, but they don't turn into a mash as berries and you don't have to shell them as nuts... and unlike a jackfruit for instance, (which is also totally unpractical to carry around, unless it's pre-cut), these small fruits are also not so easy to overeat of, as the taste is more intense and you need less, and ingest far less sugars.
