Combine juice, cumin, and pork in a medium bowl, tossing well to coat. Let stand 5 minutes.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add pork to pan; sauté 4 minutes or until done. Remove from pan.
Recoat pan with cooking spray. Add peppers and onion; cook 6 minutes or until tender. Add garlic and pork; cook for 1 minute. Add 1 tablespoon soy sauce and sugar; cook 1 minute. Remove from heat.
Warm the tortillas according to package instructions. Serve pork mixture with tortillas, mango, and sour cream.