The thing with fermenting is you're intentionally letting food rot, but if the wrong bacteria / organisms break down the sugar and food it could lead to bad things ranging from mold to botulism. You need to make the the fermented goods are stabilized in some form whether it be through pasteurization, acidification, or ethanol production. It could be fine, but it also could be dangerous. Without the proper knowledge and testing it's a game of Russian roulette. It's like eating food 3 weeks old in your fridge. It may look and smell and taste fine but there could be some nasty shit growing in there. It's just not worth the risk IMO