In a large cup or mason jar, add in the freshly squeezed lime juice, lime zest, mint leaves, and sugar. Note: don’t skip the lime zest, it adds a ton of flavor without the bitterness of the white rind. Most people like to mash up slices of limes. I find that it makes the drink bitter very quickly, so the zest fixes the issue while keeping great flavor!
Use a muddler to mash up the mint leaves to extract flavor. Tip: if you don't have a muddler, you can use the thin end of a wooden spoon instead.
Now fill the rest of the cup with ice. (About 1 cup of ice).