Can you cheat a fingernail drug test?

Not really. The only way to cheat it would be to pull off all your fingernails. Painful. Even if you clipped them back to the quick (including toenails) the testing would just have you come back later with instructions to not clip or chew your nails. If you did clip/chew before the next test they would just fail you for refusing to give a sample.

The test isn’t for things on the outside of the nail. It is for the things inside the nail. When you do drugs, the various metabolites get into the keratin of the nail and stay there. Just the same with hair. They can remain there for months.

Best answer: stop doing the drugs for about 10 months, keep your nails trimmed for the entire time.

No. I also wouldn’t advise on how to cheat a system or how to cheat to get something you do’t deserve. Imagine you owned a company and put a test in place only to find out every person you hired cheated the system.
Do the right thing.