Sean Cleathero, 28, was advised to dissolve a sachet of the drug Dinitrophenol (DNP) in water before he drank the concoction at a gym in Buckinghamshire.
Jamie Chivers, 44, Jason King, 41, and Peter Purkins, 47, all denied the 28-year-old's manslaughter on October 16, 2012.
Following a trial at the Old Bailey, Mr Purkins and Mr King were found not guilty of killing Mr Cleathero.
The jury was discharged after it failed to reach a verdict on Mr Chivers, of Spring Gardens Road, High Wycombe.
He will face a two-week retrial on November 24.
The court heard Mr Chivers had already admitted perverting the course of justice as well as the production and supply of anabolic steroids, a class C drug.
Mr King, of Prestwood, Great Missenden, and Mr Purkins of Hazlemere, will face a separate retrial on February 2 next year on charges of the supply and production of anabolic steroids.
Mr King will also be tried again on a charge of perverting the course of justice.
Their co-defendant Laura Hague, 23, of Orchard Grove, Chalfont St Peter, was found guilty of supplying anabolic steroids and perverting the course of justice.
She was remanded in custody to be sentenced at a later date.
DNP is not a controlled drug because it has a legitimate use as an insecticide or herbicide, but it is not fit for human consumption.