Cut the passion fruits in half and scoop the pulp into a bowl. You should have about 1 cup of pulp from 8 to 10 ripe passion fruits. Reserve a small spoonful of pulp and seeds for garnishing, if desired.

Transfer the pulp to a blender with 2 cups of cold water. Blend on low speed for a few seconds, just enough to loosen the pulp from the seeds without crushing them.

Pour the mixture through a fine-mesh strainer or cheesecloth into a large pitcher. Gently press the pulp with a spoon to extract the juice, but do not force the seeds through the strainer. Discard the remaining seeds and pulp.

Stir in the remaining 1 cup of cold water and ¼ to ½ cup of sugar until fully dissolved. Adjust the sweetness to taste.

Add the lime juice and stir to combine.

Refrigerate for at least 1 hour. Stir before serving, then pour over ice, if desired.

Garnish with a lime slice or the reserved passion fruit pulp and seeds, if using.