Credit: Peggy Sirota/GQ

Even squeaky clean teen stars get curious.

In the June issue of GQ, 18-year-old Justin Bieber admits occasionally drinking alcohol, despite being underage. "For me, it's just like, I like to be in control of myself. I mean, I've had a beer, like, before. . . But I never get out of control."

A large part of that decision stems from not wanting to disappoint his fans -- or his tight-knit team. Scooter Braun, Bieber's manager, says the "Boyfriend" singer "knows that I hold him to a high standard. He doesn't want to blow it."

Explains Bieber: "I mean, I keep my guard up a lot, because you know, you can't trust anyone in this business. That's what's sad. You can't trust anybody. I learned the hard way."

The Canadian pop star -- who tells GQ he's "never made a bad song" -- also defends reality star and longtime pal Kim Kardashian, 31, after a member of his entourage says the "bitch should never wear white in public again."

"You guys are so mean, bro," Bieber tells his tour manager Allison Kaye. "People say she doesn't do anything; she actually does do stuff. She works hard."