Place the vinegar in a small, heavy saucepan and bring to a boil over medium-high heat. Reduce the heat to low and gently simmer until the vinegar reduces to about ¼ of its original volume, about 20 minutes. Check the consistency: It should be syrupy and coat the back of a spoon. Simmer slightly longer if needed.
Remove garlic’s aroma from your fingers by rinsing them with water and then rubbing them against any stainless-steel surface, like the back of your knife.