Found growing in someone's garden in the rain forest of Chiapas, Mx. Mature fruit is small, less than 2 cm, yellow, sweet, and sort of insipid. Physalis maxima is found in the region, but it doesn't seem to resemble the plant in this photo. Note the trifoliate leaves, margin not dentate. Does anyone recognize this plant, or willing to hazard a guess?
Possibly a variety of physalis peruviana - goldenberry, Cape gooseberry. There are lots of physalis cultivars out there, and it can be difficult to identify. The photo looks a lot like the larger "tomatillo" fruit, but your description indicates a small sweet fruit. Here is a link to physalis names I found on the web. I hope it's ok to post the link. I grew tomatillo here in Mississauga, Ontario - the plants got to be 6 feet tall and somewhat gangly,like in the photo. They had yellow flowers and fruit was anwhere from 1-2", both green and purple skinned varieties. The ground cherry and goldenberry plants were smaller (to 2 feet) shrubs. The hardier groundcherries (such as Aunt Molley) fruit ripened, but the physalis peruviana never ripened. Seems they need a longer growing period than what we can offer here, Zone 5B.
It looks just like the goldenberries I am growing here. Got the seeds from JLHudson. The plants are up to about four feet tall here and have produced some fruit which is auite tasty, a bit like a gooseberry.