Sources close to Kodak tell TMZ ... his team believes last month's prison fight, which left a guard injured, was all a setup because they claim someone slipped something in his drink to set him off.

We're told surveillance video shows Kodak drinking a cup of coffee about 20 minutes before the fight broke out ... and his reps believe Kodak's coffee was spiked with a chemical substance intended to make him lose control.

Our sources say an agent from the FBI testified Wednesday that witnesses said Kodak appeared to be under the influence during the brawl.

As for the fight itself ... we're told Kodak got into it with another inmate, and a corrections officer sprayed KB with mace. Our sources say it took several prison guards to restrain Kodak, who displayed incredible strength after allegedly being drugged.

Bureau of Prisons spokesperson Emery Nelson tells us a staff member was physically assaulted during the fight and was taken to a hospital for treatment.

As we reported ... Kodak was sentenced Wednesday to 46 months in prison after pleading guilty in his federal gun case. Prosecutors were gunning for 96 months after KB was involved in the fight.

Kodak's camp thinks it's suspicious the other inmate in the fight was placed in KB's prison pod earlier in the day, and the same inmate was released on bond about 12 hours after the brawl. Kodak's team says the fact the fight went down 2 weeks before his sentencing is also fishy. KB's been behind bars before, and we're told it's the first time he got in trouble.

Black's reps tell us they don't know for sure who allegedly drugged him, but they have their suspicions ... telling us a lot of people want to see him jammed up.

We reached out to the U.S. Attorney's Office ... but they have no comment.