My son has mastered saying "Thank You" at the appropriate times. When given food, toys, something, anything, you gonna get "Thank You".
More like a "Tank You" at this stage.
He also says "No Thank You" when he is done eating and asked if he wants more. Also when he is offered something and does not want it.
With no real idea of the power of sarcasm, he also says "No Thank You" when he doesn't want something done to him, like...
Diaper change, putting on his coat to leave the house, taking the tablet from him, anything that will advance the day along that he feels is not important, your gonna get the nicest "No Thank You".