Step 1: Prepare the Grapes

1. Rinse the grapes thoroughly under cold water and pat them dry with a paper towel.
2. Remove any stems from the grapes and place them in a large bowl.

Step 2: Make the Sour Coating

1. In a separate bowl, mix the lemon juice, granulated sugar (or sugar substitute), citric acid (if using), and a pinch of salt until the sugar is dissolved.

Step 3: Coat the Grapes

1. Pour the sour mixture over the grapes and gently toss to coat them evenly.
2. Let them sit for about 5–10 minutes to absorb the flavors.

Step 4: Freeze the Grapes

1. Line a baking sheet with parchment paper. Spread the coated grapes in a single layer on the baking sheet.
2. Place the baking sheet in the freezer and freeze the grapes for 2–3 hours, or until completely frozen.

Step 5: Serve

1. Once frozen, transfer the grapes to a resealable bag or container for easy snacking.
2. Enjoy them straight from the freezer for a refreshing treat.