...if you're specifically talking about modern malic-acid flavors, that technology wasn't developed until the mid-seventies in east asia and wasn't imported stateside until the early nineties, but it was an immediate hit and quickly swept through the domestic sour-candy market, with most brands offering 'extreme' variants of their existing products...

...i can't recall any time when sour candy wasn't a major product sector and a quick perusal of candy history essays shows it dating back nearly as long as manufactured candy has been a thing, with a history of sour preserved confections before that...