Heat 1 teaspoon vegetable oil in a large nonstick skillet over medium heat. Add chopped spinach, and stir-fry for 1 minute or until wilted. Remove from pan, and keep warm.
Heat 2 teaspoons oil in pan over medium-high heat. Add shrimp and bell pepper; stir-fry 2 minutes. Combine sake and the remaining ingredients. Add sake mixture to shrimp. Bring to a boil; cook 1 minute. Serve shrimp over spinach.