Put meat in crock pot. Pour soup; onion soup mix over meat. Add Diet Sprite/7up/Sierra Mist. Cook in crock pot all day on low (or high for at least 4 hours). Turn off and let sit for 30 minutes before serving. {If you want thicker gravy, you could remove meat, place gravy in a skillet with a little cornstarch and heat until thickened. I didn’t do this.)