Prepare all the ingredients.

Put the sugar into a small saucepan and pour in a cup of water.

Bring to a boil and then remove from the heat.

Cut the lemons in half.

Squeeze the lemons for juice — you should end up with about a glass of juice.

Pour lemon juice into a large pitcher with ice.

Add sugar syrup.

Add carbonated water to chill the lemonade more.

If the lemonade is too sweet, add more water.

Serve on a hot day, placing a lemon slice in the glass for garnish.