What is it called when athletes ingest dietary supplements that, unbeknownst to them, can result in a positive test for banned substances?

Answer: inadvertent doping

Doping is the use of drugs or a specific methods to increase the performance of an athlete during a competition.

On the other hand, inadvertent doping means that the athlete didn't take the drug, that resulted in positive test, through deliberate planning. This unintended situation was probably due to some supplement that the athlete took and he didn't know what it contained.