At the launch event of the futuristic vehicle last week, Mr Musk described the truck's body as "literally bulletproof" and invited Tesla's head of design Franz von Holzhausen to hit the door panels with a sledgehammer.
The ultra-hard steel, which is made out of the same alloys found on spacecraft, resisted the strikes without weathering any significant damage.
Mr Von Holzhausen was then asked to throw a small metal ball at the driver's-side window, with the expectation that it wouldn't even crack.
"Oh my f****** god," Mr Musk said when the ball smashed the glass. "Well, maybe that was a little too hard."
The Tesla boss blamed the order in which the demo took place for the mishap, which has been viewed millions of times and widely mocked online.
"Sledgehammer impact on door cracked base of glass, which is why steel ball didn't bounce off," Mr Musk tweeted. "Should have done steel ball on window, *then* sledgehammer the door. Next time."
Despite the apparent mishap, Tesla has already received more than 200,000 orders for its Cybertruck since it was unveiled on Thursday night.
Mr Musk also explained the reason for the unusual angular design of the Cybertruck, claiming that current auto manufacturing technology is not capable of bending the ultra-hard material.
"New manufacturing methods are certainly needed, but then I'm confident it will actually cost less, because of its simplicity and lower part count," he tweeted.
The space-age design has proved divisive but received praise from Blade Runner artistic director Syd Mead, who described it as "stylistically breathtaking".
During the truck's unveiling, Mr Musk said: "Trucks have been the same for like 100 years. We need something different."
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