DIY Sour Frozen Grapes

In a large bowl, combine 4 cups seedless grapes with the juice of 3 lemons (about 6 Tbsp.). Toss to combine. In a separate bowl, combine ¼ cup sugar with 2–3 tsp. food-grade citric acid or 12–16 packets TrueLemon. Roll each grape, one at a time, in the sugar-citric acid mixture until evenly coated. Freeze in a single layer on a parchment-lined rimmed baking sheet for at least 2 hours. You can enjoy them right away, or transfer them to an airtight container for up to 3 months in the freezer.