The drinks company founder was axed by Lord Alan Sugar after Team Sterling lost this week's fitness challenge, in which professional wrestler Ricky Martin served as project manager.
The group's 'Beat Battle' workout, a combination of mixed martial arts and street dance, achieved total sales of £7,970 from three health club chains.
Stephen Brady's Phoenix, however, collected £12,810 from a single deal for their retro 'Groove Train' routine.
Watch Digital Spy's interview with Duane Bryan below:
In the boardroom, it emerged that Sterling lost because the promising concept of 'Beat Battle' wasn't executed properly. Karren Brady added that their promotional video appeared dull in comparison to Phoenix's clip, which featured Azhar Siddique in tight shorts performing exercises on space hoppers.
Bryan and Laura Hogg, who directed and starred in the promo respectively, were brought into the boardroom by Martin for failing to demonstrate the martial arts element of the routine, weakening the product.
However, Bryan defended both himself and Hogg, stating: "Laura shouldn't be here. She came and delivered, she contributed."
He also accused Martin of "trying to pass the buck", while the businessman-come-athlete blasted Bryan for getting too "emotionally involved".
In delivering his verdict, Lord Sugar noted that Hogg had been brought back into the boardroom just one week after almost being fired, but gave her another chance after deciding that she was not responsible for the task's failure.
He continued to criticise Martin's choice of boardroom companions, saying that he had made a "very, very bad management move", but finally opted to send Bryan home.
"You put yourself forward to product the video, I personally believe that the video was the main cause of the failure of this task," Sugar said. "And therefore Duane - you're fired."
Speaking on his way out of the boardroom, Bryan accepted: "Lord Sugar knows what he wants and unfortunately this time it wasn't me.
"That's not going to take anything away from me, I've got a lot to give, a lot to prove and I'm going to go out there and do that. I'm hoping that you've not seen the best of me yet."
The Apprentice continues next Wednesday at 9pm on BBC One.
> 'The Apprentice' episode five review: 'They call me the fitness'