Prepare the sardines by removing the heads and back bones. Rinse and pat dry. Coat in flour, shaking off any excess.
Heat the olive oil (reserve about a tablespoon) in a large frypan over medium-high heat. When the oil is hot, fry the sardines a few at a time until brown and crispy. Remove to a large serving plate, and keep warm.
In another frypan over medium heat, heat the remaining oil. Add garlic, and cook for about half a minute. Add the wine and vinegar, and allow the mixture to simmer, stirring occasionally. When the liquid has reduced by about half, pour the sauce over the sardines, and sprinkle with fresh mint. Let stand for about 1 hour before serving to allow the fish to marinate.