Since someone applying at MEPS isn't even in the military, obviously the military would have no authority to punish someone for anything. Until the contract is signed, the person isn't under the UCMJ.
By "without punishment" I mean "without losing a job offer you would have otherwise had."
The person volunteering has to provide various documents, take a battery of written tests, get physically examined, have a urinalysis done, and have a background check done.
See: how well you can lie. People study up for their tests even though you're not supposed to, lie their tails off on the physical questions, etc. I don't know when you knew someone going into the military, but nowadays you see kids lying about EVERYTHING. No kid wants to lose out on a paid college education and a job because they had an asthma attack when they were 14: so they lie their teeth off, and not just about drug use.