Gently pull each grape from the stem and transfer to a colander; rinse under running water.
Transfer grapes to a shallow dish and pour the Prosecco and vodka over them, making sure the grapes are covered in the liquid.
Cover the bowl and place in the fridge for at least 8 hours (preferably overnight.)
Pour the sugar in a shallow bowl.
Drain the grapes, but don’t let them dry completely. Place a handful at a time in the sugar and roll/toss to fully coat them.
You can serve these right away, but they're best when they've chilled for a couple hours before eating. It's fun to serve them in a champagne coup glass or bowl, and also threaded on party skewers.
