Examples:

I don't know jack about computers.

He's not worth jack. He doesn't know anything.

She pretended to know jack about art, but it was obvious she was faking.

If you don't know jack about cooking, don't try to make a gourmet meal.

I don't know jack about cars. Can you help me change a tire?

He's a total fraud. He doesn't know jack about business.

I don't know jack about politics. Who is running for president?

She's pretending to be an expert, but she doesn't know jack about the subject.

If you don't know jack about gardening, don't try to grow a vegetable garden.

He's a complete idiot. He doesn't know jack about anything.

I'm not going to ask him for advice. He doesn't know jack about relationships.

She's a total fraud. She doesn't know jack about art history.

Don't ask me about technology. I don't know jack about it.

He's pretending to be a financial expert, but he doesn't know jack about investing.

I don't know jack about cooking. Can you recommend a good restaurant?

She's a total fraud. She doesn't know jack about music theory.

I don't know jack about sports. Who won the Super Bowl?

He's pretending to be a fashion expert, but he doesn't know jack about style.

I don't know jack about cars. Can you help me change a flat tire?

She's a total fraud. She doesn't know jack about psychology.

Rahul claims to have a lot of programming experience, but I’m pretty sure he doesn’t know jack about databases.