We're already aware of the punishing workout regimen Sylvester Stallone subjected himself to in order to achieve Rocky Balboa's ripped physique, but his on-set diet was perhaps even more grueling.

The now-70-year-old-Stallone recalled drinking 25 cups of coffee every single day while filming 1982's Rocky III to make up for the brutal energy deficiency he experienced from living off his dizzyingly high-protein, low-carb diet.

"I was on a very high protein diet which did not provide much physical or mental energy," Stallone captioned the photo.

"During the period I only ate very small portions of oatmeal cookies made with brown rice and up to 25 cups of coffee a day with honey and a couple of scoops of tuna fish."

With a body fat percentage of just 2.9 percent—that's down to elite bodybuilder levels—Sly had to engage in some crazy antics to maintain the focus needed to execute the fight choreography, hence the headstand pose in the Instagram photo above.

"...Getting smashed by super-strong Clubber Lang continuously four months of rehearsal, plus the fight, tended to wear a person out," Stallone recalled.

"I would literally go to the corner between rounds when I wasn't directing and try to get some blood back into my head so I could carry-on with the complicated fight choreography."

Just more proof that Sly definitely has the "Eye of the Tiger."

h/t: NY Daily News