Step 1: Season the chicken - Start by patting your chicken thighs dry with a paper towel. This helps them brown better later. Sprinkle the salt, black pepper, and garlic powder evenly over each piece. Take a moment here to really coat them well. This simple seasoning step builds the foundation of flavor.
Step 2: Sear for flavor - Heat the olive oil in a large skillet over medium heat. Once the oil is warm, place the chicken thighs skin side down. Let them cook undisturbed for a few minutes until the skin turns golden brown. Flip and brown the other side as well. This step is worth it. It adds depth and a rich flavor that you just cannot get from slow cooking alone.
Step 3: Transfer to slow cooker - Place the seared chicken thighs into your slow cooker. Arrange them in a single layer if you can so the sauce can coat everything evenly.
Step 4: Make the sauce - In a bowl, whisk together the Sprite, sweet chili sauce, soy sauce, brown sugar, and cornstarch. Whisk until everything is smooth and combined. You should see a slightly glossy mixture already forming.
Step 5: Pour and coat - Pour the sauce over the chicken thighs in the slow cooker. Make sure each piece gets a good coating. You can gently move the chicken around to help distribute the sauce evenly.
Step 6: Slow cook to perfection - Cover and cook on low for 5 to 6 hours. During this time, the chicken becomes tender and the sauce starts to thicken.
Step 7: Finish and thicken - During the last 30 minutes, remove the lid from the slow cooker. This allows the sauce to reduce and thicken into a beautiful glaze. Before serving, spoon the sauce over the chicken to coat every piece.