Place wine, grape juice, and apple juice in a medium-sized bowl. Dissolve sugar in warm water and add to bowl. Whisk together for one minute until well mixed.

Pour into a nine- by 13-inch (20- by 30-centimeter) baking pan. Place in the freezer. Using a fork, stir the mixture every 30–45 minutes, scraping edges and breaking up any chunks as the mixture freezes. Do this three times.

When it’s almost frozen, mash it with a fork until granita is slushy and has the right texture. Return to the freezer until serving.

To serve, scrape with a spoon or mini scoop. I like serving it in small wine cups with diced fruit at the side.