Salt

He picked up the salt cellar and shook it all over his chips. The top came off and there was a week or more's worth of salt on his supper.
He started to scrape it off.
"Err, what do you think you're doing?" asked his mother.
"I was just..."
"No. Eat it."
He started eating the overly-salty chips. He was getting thirsty. He stood up.
"Where are you going?"
"To get a drink. I'm so thirsty."
"Sit back down. No drink before you finish eating."
He sat and continued to eat. Tears streamed down his face. His mouth felt like a desert and his chips tasted terrible.
Eventually he finished and went to get a drink.
"Did that teach you anything?"
He thought for a second and then threw the glass straight at her head.