How to Make a Refreshing Watermelon Mojito at Home

The Simple Syrup Ratio

I use a 1:1 simple syrup — equal parts sugar and water by volume. This is standard, but I want to emphasize the temperature. Bring the water and sugar to a gentle simmer, not a rolling boil. A full boil can caramelize the sugar slightly, adding a cooked flavor that competes with the fresh watermelon. Once the sugar dissolves completely, take the pan off the heat. Let the syrup cool to room temperature before using. Hot syrup will wilt the mint and thin out the drink.

If you want to skip the syrup, you can muddle a teaspoon of granulated sugar with the mint and lime. It takes a bit more elbow grease to dissolve, but it works in a pinch.

Building the Drink

Once the mint mixture is ready, divide it between two highball glasses. Add the watermelon juice. If you're using rum, pour it in now. Stir once gently to combine — you want the flavors to marry, but you don't want to knock the carbonation out of the club soda that's coming next.

Crushed ice is the right choice here. Cubes are too large and will melt slowly, leaving you with a drink that's not cold enough. Crushed ice chills quickly and dilutes at a steady pace. I fill the glasses all the way to the top. Then I pour in a splash of club soda — about a quarter cup per glass. Stir once more, very gently.

The garnish is more than decoration. A mint sprig placed so the leaves are near the rim lets the drinker catch that herbal aroma with every sip. A thin lime wheel adds a visual cue and a hint of extra citrus if someone squeezes it in.

Making It a Mocktail

This drink works beautifully without alcohol. Simply omit the rum and add an extra splash of club soda or a bit more watermelon juice. The bright flavors stand on their own. I often make a pitcher of the non-alcoholic version for parties, then let guests add rum if they want. Just keep the juice and mint mixture separate from the ice and soda until serving, or it will go flat.