Britney Spears, who was filming the promo for new single Give Me More, apparently looked "dead-eyed" and "disorientated" and became paranoid during her raunchy pole dance last Wednesday.
A source said: "Britney was rude, and she chain-smoked and drank an enormous amount of Red Bull throughout the shoot.
"She had a problem with the extras watching her pole dance, suddenly she was in floods of tears. It was sad to witness."
At one point, Britney - who was wearing a black leather waistcoat, a pair of black hot pants and ripped fishnet tights - squatted on the floor and hugged her Yorkshire Terrier puppy London as she vacantly stared into space.
Around 100 frustrated crewmembers were sent home after 18 hours on the Los Angeles shoot, which had been paid for by Britney.
The 25-year-old star is desperate to re-launch her ailing pop career since splitting from husband Kevin Federline, shaving her head and entering rehab.
The video shoot took place just hours after Britney's shocking interview and photo shoot with America's OK! magazine, during which the mother-of-two was said to be "completely out of it".
Her mood was described as erratic and she was reportedly extremely paranoid - at one point believing the ceiling was about to cave in.
Britney ordered fried chicken during the shoot and wiped her greasy hands on a Gucci dress worth several thousand dollars.
The singer also used a Chanel dress to clean up her puppy's faeces.