For fresh mango juice, peel mango and place the flesh in a blender. Add a splash of lemon or lime juice and blend until smooth. Strain the juice through a fine-mesh sieve. For fresh passionfruit juice, cut ripe passionfruit in half and scoop out the flesh. Press the flesh through a fine-mesh sieve set over a bowl. Use the strained liquid for the juice; reserve the seeds for garnish.