In a large bowl, whisk the egg whites at high speed until they turn white and stiff peaks form. Lower the speed to medium and add the sugar mixture, 1 tablespoon at a time; wait 30 seconds between additions. Once you’re done adding the sugar, whisk for another 4 minutes at high speed, until your meringue is hard and bright. Add the vinegar and whisk for 2 minutes at high speed. Make sure you mix well.