1-First Step: Prep the fruit and herbsStart by cubing and deseeding the seedless watermelon. You will need 12 cups total, so this is a good time to make sure the pieces are bite-sized and easy to blend. Wash the cucumber well, then cut it in half. Set one half aside for slicing later and chop the other half for the puree.Rinse the mint leaves and pat them dry. Fresh mint gives this drink its signature cool aroma, so choose leaves that look bright and lively. If your mint is especially fragrant, it will make the final pitcher taste extra fresh. For a stronger mint flavor, you can also lightly muddle it instead of pulsing it in the blender later.

2-Second Step: Blend the watermelon and cucumberAdd the watermelon and half the cucumber to a blender. Blend until the mixture is smooth and juicy. The goal here is to break down the fruit enough to release all that pretty pink liquid while keeping the flavor clean and bright. If your blender is small, work in batches so you do not overload it.Once blended, strain the mixture through a fine mesh strainer into a bowl or pitcher. Press gently to get the juice through, but do not force too much pulp into the liquid if you want a smoother drink. Set the strained juice aside while you move on to the next step.

3-Third Step: Add lime and mintPour the strained juice into a pitcher if it is not already there. Add the fresh lime juice and the mint leaves. Pulse the mixture or stir well to help the mint release its flavor. If you want a cleaner finish, strain the mixture again into the pitcher. If you like a little texture, leave a bit of the mint in place.This is the point where the drink starts to taste like a true cucumber watermelon mojito. The lime wakes up the watermelon, while the mint adds that cool, breezy note. If you are making the non-alcoholic version, this step works exactly the same, just with sparkling water instead of rum later on.

4-Fourth Step: Stir in the rum and simple syrupAdd the white rum and simple syrup to the pitcher. Stir well so the sweetness is evenly mixed through the drink. Taste the mixture if you like and adjust slightly with a bit more syrup or lime juice, depending on how sweet or tart your fruit is. Some watermelons are naturally extra sweet, and some need a little more help from the syrup.At this stage, the mixture can go into the fridge until you are ready to serve. This rest time helps the flavors mingle and gives you a chilled base that is easy to pour later. If you are feeding a crowd, this is a great make-ahead moment.

5-Fifth Step: Chill until serving timeRefrigerate the pitcher until you are ready to serve. For the best texture, do not add the club soda or sparkling water yet. Keeping the fizz out until the last minute helps the drink stay lively and bright.

6-Final Step: Add bubbles, serve, and garnishRight before serving, stir in club soda or sparkling water, along with the remaining cucumber slices. Then fill your glasses with ice and pour the drink over top. Finish each glass with watermelon slices, lime wheels, and mint sprigs for that polished, party-ready look.Serve immediately while the bubbles are fresh. The cold ice, the juicy fruit, and the sparkling finish all work together to make each sip feel crisp and bright. If you want a slightly sweeter drink, add a touch more simple syrup at the table. For a lighter version, top with more sparkling water and less syrup.