The first time your baby picked up her cup and launched it across the room, you probably laughed right along with her. While it's certainly impressive that your little one has discovered the joy of throwing things, it's probably not cute any longer when she tosses her cup to the floor. It's also not good table manners, so it's essential to take action now to teach her that throwing things at the table isn't allowed.
Tell your child "no." Use a firm and authoritative but gentle voice when your baby throws her cup. Tell her that she is not allowed to throw her cup and show her how to place it on her highchair tray or the table when she's done with it. Be consistent, too. Say "no" every time she tosses the cup so she gets the message that it's not allowed.
Take your baby's cup away from her. Give your baby one chance by telling her that if she throws her cup again, you'll take it away. If she does launch the cup again, immediately pick it up and put it out of your baby's reach. Over time, she'll learn that throwing her cup means she won't get to have it on her highchair anymore, and that can cut down on the behavior.
Take charge of your baby's cup. Instead of giving your baby the cup, keep it out of his reach near your own plate and cup. When he indicates that he's thirsty, you can hand him the cup and then take it back when he's done. The less time your baby has the cup in his grasp, the fewer opportunities he'll have to toss it.
Distract your child. If your little one has been gleefully enjoying throwing her cup, giving her something else to concentrate on can stop the behavior. Offer your baby tiny cubes of food or give her a piece of paper and a crayon so she can scribble while she waits for the meal to start.
Ignore your baby's behavior. Yes, it will be difficult, especially if you're already annoyed with the cup throwing, but if your baby doesn't get a response by throwing her cup, she's more likely to stop doing it in the future.