For the Limeade

Combine the sugar and 1 cup of water in a small saucepan to make a simple syrup.
Cook the water and sugar mixture over medium heat until the sugar has dissolved, stirring frequently. Allow the simple syrup to cool.
In a 2 quart pitcher, combine the simple syrup, fresh squeezed lime juice, and the cold water - starting with 4 cups and then tasting.
Adjust water according to your sweet taste preferences by adding more water if desired (up to 2 additional cups is usually a good amount).
Transfer the prepared limeade to the refrigerator. Chill.This will make extra limeade so feel free to use the rest for drinking or to make additional slushes.

For the Cherry Limeade Slushies:

Combine the 2 cups limeade, crushed ice, and the frozen cherries in the jug of your favorite blender.
Start with 1 cup of crushed ice and add an additional cup for a total of 2 cups until desired slushy-ness has been achieved.
Puree the limeade, ice, and frozen cherry mixture until blended to slushy consistency.
Divide the cherry limeade mixture between 4 glasses.
Serve immediately.

NOTES

Frozen Cherry Limemade Slushie Tips

Do I have to make homemade limeade? Absolutely not! When I don't have time, I use Simply Limeade that I buy at my grocery store.
Can I substitute something else for cherries? You can use any fruit you like as long as it goes well with lime! I recommend strawberries, raspberries, blackberries, blueberries, or pineapple.
Can I use lemons instead of limes? If you want to make homemade lemonade, just swap out the limes and use the same amounts of lemon juice.
Can I make an adult beverage out of this? Yes, add a total of 4 - 6 shots of vodka or tequila to the blender for a frozen cocktail. Do not serve alcoholic beverages to anyone under the age of 21.