Kind of an interesting concept, but far from reality. Drug testing celebrities or entertainment industry members before an award show is probably a futile exercise. In all probability, during the window of time of entering the ceremony to the actual award acceptance some can sneak a substance or pill before hitting the stage. Especially, when these award shows are extremely long.
The Screen Actors Guild does not need to conduct drug testing prior to actors accepting SAG awards. If these actors want to use drugs, that is their own business. It is not up to SAG to police the lives of actors. The government already does too much of that in all our lives.
Lots of artists use drugs. That's just the truth of it. There is also a lot of debate as to whether these drugs should be legal. If a person is on drugs while they win an award, that doesn't mean that they didn't win the award. They should be allowed to accept what they won.
No, SAG has no business testing award recipients as a condition of letting actors take the stage. There are many legitimate reasons why an actor may exhibit unusual facial expressions, such as method acting, playing a character in the real world that they have or will be portraying in an upcoming production; side effects from prescription medication; or deliberately being silly or strange. Even if Ryder was high at the time and looked foolish, that's on her.