Is there a pill or food that would make you test positive for marijuana?

Any drug that contains THC (e.g., Marinol) and any food that contains marijuana (e.g., "weed brownies") will cause a positive THC test.

However, there are some products that can cause a false positive for THC, such as ibuprofen (Advil, Motrin, etc.), naproxen (Aleve), hempseed oil, and even riboflavin (vitamin B2).

This does not mean that taking those products will cause a false positive. Sophisticated drug tests won't be fooled.