• Spray a 6-quart slow cooker liner with cooking spray.
• Combine the honey, water, soy sauce, and balsamic vinegar in a small bowl.
• Set pork tenderloin in the slow cooker, with the fatty side facing up.
• Pour honey mixture over the meat and sprinkle with the garlic powder and pepper.
• Cook on high for 2-3 hours or low for 4-6 hours. Use an instant-read thermometer to confirm the pork is at least 145°F before serving.

Make sauce:

• In a small bowl, whisk together the soy sauce, honey, balsamic vinegar, and cornstarch. Ensure there are no lumps.
• In a small saucepan, heat olive oil. Add garlic and sauté for 30 seconds, stirring constantly.
• Add the soy sauce mixture and stir until it boils. Continue at a rolling boil for 2 minutes, stirring constantly, until slightly thickened.
• Slice pork tenderloin and place on a serving platter. Drizzle with sauce or serve on the side. Add chopped green onions as garnish if desired.