In a gallon ziplock bag combine the Sprite, soy sauce, garlic, thyme and lemon juice and set aside in a large bowl so it won't spill over.
Place each chicken breast into a large ziplock bag and using a rolling pin or flat side of a meat tenderizer, pound chicken breast until even thickness. About 3/4 inch thick.
Add the chicken breasts to the marinade, close the bag tightly and gently shake around to completely coat the chicken.
Place the bag back into the bowl and leave on the counter for 30 minutes to marinate. If you need to marinate it longer, place in the refrigerator for up to 2 hours. Do not marinate longer than 2 hours.
Preheat a grill to 400 degrees.
Place each breast onto the grill top side down. That would be the side with what used to have the skin on.
Close the lid and let the chicken cook for 6 minutes.
Turn over and cook for an additional 4-6 minutes until the center is no longer pink.
Place onto a plate, loosely cover with foil and let it rest for 10 minutes while you make the next step.
In a small bowl mix together melted butter and lemon zest.
Using a silicone brush, brush butter onto each chicken breast. Make sure to get the lemon zest onto the chicken as well.