caffeine

例句：

1. 1. She added a cup of coffee to her morning routine.
   她在她的早晨例行公事中加了一杯咖啡。
2. 2. The caffeine in the coffee can be addictive.
   咖啡中的咖啡因可能是上瘾的。
3. 3. I need some caffeine to stay awake during the long flight.
   我在长途飞行期间需要一些咖啡因来保持清醒。