Bring water and sugar to a boil in a small saucepan, stirring until sugar dissolves. Add passion fruit pulp, stirring well, and cook 1 minute. Remove from heat; cool 15 minutes.
Strain passion fruit mixture through a sieve into a large bowl; discard seeds. Add lime juice, soy sauce, red pepper, and salt, stirring well. Set 1/2 cup passion fruit mixture aside. Add shrimp to remaining passion fruit mixture, and toss well to coat. Cover and refrigerate 15 minutes.
Thread 4 shrimp on each of 8 (10-inch) skewers. Place skewers on grill rack coated with cooking spray. Grill 2 minutes on each side or until done, basting with reserved 1/2 cup passion fruit mixture. Serve with lime wedges.