I think it depends on the barrio. For example, if you go to some of the higher income barrios, Recoleta, Barrio Norte, Belgrano, yes there is still junk food around however there are healthy snacks all over such as cereal bars, granola, wheat crackers, mixed nuts, trail mix and a lot of dieteticas. If you go to some lower income areas the offerings are mostly low quality alfajores, all kinds of cheap candy and lots of sodas and sweetened beverages. However the same applies in New York City where I come from, on the upper east and upper west side, you can get junk food too, however there are tons of health food stores with a huge variety of healthy sweets, if you go to the south bronx, hardly any health food stores and mostly corner "bodegas" as we call them that sell Twinkies, hostess cakes, all kinds of sodas, chips, etc. Some of this about giving sweets to kids has to do with tradition but it also has to do with nutritional education.