In a small pan over high heat, combine sugar and water; bring to a boil, stirring, until sugar is dissolved; then boil for 5 minutes.
Remove from heat and pour over mint; cover and chill for about 1 hour.
Then pour syrup through a wire strainer and discard mint.
Stir in orange juice and lemon juice; cover and chill thoroughly.
To serve, pile melon balls in a serving bowl, arranging them in layers, if desired.
Pour chilled syrup over melon and garnish with mint sprigs.
Spoon into individual bowls to serve.