Random Riddle: Defy Gravity

The following is an advertisement for a common item. The ad agency, however, is trying to entice buyers by making the item sound more impressive than it really is. Can you tell what is being sold here?

DEFY GRAVITY!
As you command water – or any liquid – to flow upwards! Could you be tampering with the secrets of the Earth? Your friends will be amazed! Just $1.99.
 

Random Riddle: Defy Gravity