In a small bowl, make the sauce by mixing together the black vinegar, sugar and soy sauce.
Heat the oil in a large frying pan until very hot. Add the eggs, one at a time (keeping them apart). Fry on both sides until the whites are crispy and the egg yolks are semi-set. Remove from the pan and set aside.
Add the sauce to frying pan and turn the heat down to low. Add the eggs back into the pan and coat with the sauce. Serve immediately.