Can you fail a drug test through sweat transfer?

Yes, you sweat out certain wastes, and they may be toxins. But these are in trace amounts, and therefore have not been proven to have any real effect; the main way for the body to excrete toxins is through urine and feces. Sweat without proper rehydration actually slows down the toxin filtering rate of the liver and kidney.

However you can find information on how sweating can reduce pesticides and other poisons in our bodies. For instance Dr David Schnare of the U.S.A Environmental Protection Agency showed that saunas reduce body levels of HCB (hexachlorobenzene) and PCBs (polychlorinated biphenyls) in electrical workers. He also helped drug users, victims of accidental ingestions, and those poisoned by a variety of environmental chemicals to recover with sauna detoxification.