Combine the peanut butter, water, garlic, brown sugar, cayenne and lemon juice in a saucepan. Bring to a boil, reduce heat and simmer for 2 minutes. Add salt and cool.
Boil the cabbage and beans in salted water to cover for 20 minutes. Add the spinach and simmer for 5 minutes. Add the bean sprouts and cook, stirring, for 1 minute. Drain. Place vegetables on a large serving dish. Top with the sauce and serve immediately.