Add balsamic vinegar and sugar, stir to combine, and dissolve the sugar.
Bring to a light boil, after which, reduce heat to medium-low. Let the mixture simmer, stirring occasionally, until it thickens and is reduced to about 1/2 cup, this will take about 10-15 minutes.
The sauce is ready when it's thick enough to coat the back of a spoon. Once chilled it will thicken more.
Remove from heat and allow to cool completely before serving over salads, fruits, cheese, or meat.