Making a flavorful, well-balanced meatless dish doesn't get simpler than this. Sweet mango is the right complement to the earthy tempeh. A drizzle of the sweet and salty cooking liquid is the perfect addition of moisture and brightness.
Stir together the water, mirin, lime juice, vinegar, honey, Sriracha, salt, and garlic in a 5- to 6-quart slow cooker. Nestle the tempeh into the liquid; cover and cook on LOW until heated through, 4 hours.
Remove the tempeh with a slotted spoon, reserving 1/4 cup of the cooking liquid. Cut the tempeh into 12 slices.
Divide the rice among 4 plates. Toss the spinach with the sesame oil, and place over the rice. Top with the tempeh slices and mango slices. Drizzle the reserved cooking liquid evenly over each serving.