Mauritian badminton player Kate Foo Kune, her country's flag-carrier at the 2016 Rio Olympics, was banned for two years for doping on Wednesday after failing to prove her drink was spiked.
Foo Kune, 27, tested positive for a banned steroid last year but she escaped a ban when the Badminton World Federation's anti-doping panel accepted her explanation that she was the victim of sabotage.
But after a BWF appeal against its own panel's decision, the Swiss-based Court of Arbitration for Sport said there was no evidence of foul play.
Foo Kune, the world number 105 in singles, tested positive at last year's African Badminton World Championships in Port Harcourt, Nigeria.
"The CAS panel found the athlete's assertion of intentional spiking during the 2019 African Badminton World Championships devoid of supporting evidence," said a statement from the court, announcing a two-year ban from December 15.
Doping cases are rare in badminton but at the 2014 world championships, Malaysian star Lee Chong Wei tested positive for a banned anti-inflammatory.
He later received an eight-month, backdated ban when the BWF accepted that he ingested the substance accidentally.