These super-refreshing fruit slushies are so easy to make and use just four ingredients. A quick homemade lemonade is frozen in ice cube trays for a make-ahead hack. Perfect for kids, but just as appealing to adults—especially spiked with a little vodka or gin!
Combine the sugar, mint, lemon rinds and 1/2 cup water in a small saucepan. Bring to a boil over medium-high heat, then reduce to a simmer and cook, stirring once or twice, until the sugar has dissolved, about 5 minutes.
Strain through a fine-mesh sieve into a large liquid measuring cup. Stir in the lemon juice (you will have about 1 cup liquid). Pour into an ice cube tray and freeze until solid, 6 hours or up to overnight.
Add 1/2 cup water to a blender (see Cook's Note), then add the lemonade ice cubes and the blueberries and blend until smooth. Divide between glasses and serve immediately.
Make sure to add liquid to the blender first when blending frozen items. This will help everything blend without having to stop and start a bunch of times.