Fun: why are flies attracted to beer?
Since flies are well known to like sugar, it could just be that flies like beer because they can detect some residual sugar in beer. But Dahanukar suspected that might not be the case. So she planned an experiment. She would give the flies a choice between beer and sugar water, and see which they preferred.
“We selected a pale ale, and the main reason was because pale ales have very lower sugar contents,” says Dahanukar. “So we were trying to identify other chemicals — chemicals other than sugars that taste good to flies.”
via Beer Or Sugar Water? For Flies, The Choice Is Pale Ale : NPR.
Flies like fermentation. Vinagar, beer, rotting fruit, etc.