Rinse and drain grapes, patting them completely dry with paper towels. Add to a medium mixing bowl. Add lemon juice and toss to combine.
On a baking sheet or in a shallow bowl combine the sugar (or monk fruit sweetener) and citric acid (if using). Add the grapes in batches, rolling each in the sugar mixture.
Remove to a baking rack or bowl and refrigerate or freeze until chilled, at least 30 minutes, and serve.