Muddle lime juice, simple syrup, and mint leaves using a cocktail muddler or the back of a wooden spoon to get the mint oils and flavour out of the leaves. Divide between to glasses, add peach slices, ice, and pour lemon-lime soda over to fill both glasses.

Add some booze if you like, but it tastes great on its own! Garnish with some more mint or other fruit you have on hand.