Wash fruit and, if needed, chop into pieces about 1 cm square.
Combine vinegar, sugar, salt, and fruit over medium heat. Stir to dissolve sugar and salt. Press lightly on fruit to release some juices.
Transfer fruit vinegar to a sterilized container. It can be used immediately. If not using immediately, let sit at room temperature for 24-48 hours then put in fridge, where it will keep for several months.
Vary sugar depending on type of fruit and personal taste. The vinegar can be used for many other purposes, such as a dipping sauce or topping for chicken or mildly flavored fish. You can use the vinegar on salad as is, or make a more traditional vinaigrette by whisking with oil, mustard, salt, and pepper.