Common Sense Evaluation

Artificial or natural, take your pick,
Although too much of the latter can make you sick.
 

The man approached a woman and said, “If you can solve how this works, I’ll give you a dollar.”

The man said “down” and the sachet of ketchup suddenly went down. Then he said “up” and it went up. Then he said “down”, and when it was halfway down, he said “stay” and it stayed.

How did he do this?