Since early this week when I put the gear in reverse, I'm getting a solid beeping sound. I read the owner's manual and it says it could be something on the sensors but they're perfectly clean.
It was perfectly fine till my friends came over last weekend and they sat in the car and were playing around with the shift (putting in each gears including reverse).
I don't think it's got to do with it but the next day when I pulled it out from the garage, I've been getting solid beeping sound.
Anyone knows what's going on?? any typical reasons?

 

Anything low and close off to the rear side? What about if you are out in the street well clear of everything - still solid?

 

Yes, even in an empty street.

 

Take it to the dealer

 

+1, it sounds like you might have a faulty sensor.