Rotherham forward Nico Steenkamp has received a three-month suspension after testing positive for the banned stimulant methylhexaneamine.
The Rugby Football Union punishment comes just a day after it was announced they had banned Sale Sharks prop Karena Wihongi for four months following his positive test for the same stimulant.
Steenkamp tested positive following a Championship game between Rotherham and Cornish Pirates in early January.
His ban runs from a provisional suspension date of January 28 until April 28.
The RFU disciplinary panel heard that Steenkamp had been combining working full-time as a double glazing and window installation fitter with training at Rotherham three nights a week, four or five weekly gym sessions, plus two-hour drives to and from training.
He then began taking the high-energy drink USN Anabolic Nitro in a bid to help him combat fatigue.
In its written judgement, the panel said: "We were satisfied the player did not know that Anabolic Nitro contained MHA, and there was no reasonable basis upon which he could have know that such was the case.
"In this case, the player did not in any event take Anabolic Nitro with a view to enhancing his sport performance.
"Rather, he had taken Anabolic Nitro with the intention of alleviating fatigue caused by his arduous lifestyle and its logistical demands.
"He relied on assurances from someone who was not a doctor, from the seller of the supplement and from his own efforts on the internet.
"Even when the player made good faith efforts to leave no reasonable stone unturned, he is still at fault in failing to consult a doctor or anti-doping specialist, or indeed to have the substance analysed.
"Any athlete who takes a supplement without first taking advice from those with expertise in doping control, places himself at real risk of committing an anti-doping rule violation.
"He did take what he thought were his own reasonable steps to ascertain the status of the ingredients. They were not enough."