1. Toss together first 6 ingredients and 1 Tbsp. wine. Let stand 30 minutes. Meanwhile, stir together hot water, hoisin, and remaining 1 Tbsp. wine.
2. Remove beef from marinade, discarding marinade. Sprinkle with salt and black pepper; cook half of beef in 1 1/2 tsp. hot canola oil in a large skillet over high heat, without stirring, 45 seconds or until browned; turn beef, and cook 30 seconds or until browned. Transfer to a warm plate. Repeat with remaining 1 1/2 tsp. oil and beef.
3. Stir-fry onion in remaining 1 Tbsp. hot canola oil in skillet over medium-high heat 2 minutes or until tender. Add sugar snap peas, ginger, and crushed red pepper; stir-fry 2 minutes. Add beef and hoisin mixture; stir-fry 1 minute or until slightly thickened. Remove from heat. Stir in watermelon. Add salt, black pepper, and red pepper to taste. Serve immediately with hot cooked rice.