Beat the vinegar in a bowl with the optional sugar, garlic, salt and pepper until sugar and salt dissolves. Then beat in the oil by droplets, whisking constantly or place all the ingredients in a screw-top jar and shake to combine. Taste and adjust the seasonings.
If not using dressing right away, cover and refrigerate, whisking or shaking again before use.
Can be used as a dressing and a marinade.
*If using a good quality balsamic vinegar you should not need the sugar, but if using a lesser quality you might want the sugar to round out the dressing.