Joylessly is how you do something when there is no happiness in it. You can eat joylessly, work joylessly, or even smile joylessly — a smile that is only on the face. It carries the same strong, slightly careful feel as joyless. It does not mean the person is always sad in a loud way; it often means they are going through the motions, with the pleasure missing. You will see it more in stories and news writing than in everyday speech, where people are more likely to say “with no joy” or “without any pleasure.”

毫無歡樂地；了無生趣地