Create a simple syrup by combining 1 cup of sugar and 1 cup of water in a saucepan over medium heat. Stir until the sugar dissolves and the mixture is clear. Remove from heat and let cool.

Squeeze lemons to obtain 1 cup of juice. Cut passionfruits in half and scoop out the pulp into a strainer over a bowl, pressing to extract juice.

In a large pitcher, combine lemon juice, passionfruit juice, cooled syrup, and remaining 4 cups of water. Stir well and adjust sweetness if necessary.

Chill the mixture in the refrigerator for at least one hour before serving.