Drug testing

For alcohol? You can't prove innocence unless it was same day.

For anything else...

I'd do a few hair tests if you didn't take anything. Nail tests take a long time to show positive, hair tests not as long. 

Well, how I was told... nails and hair strand tests take 7-10 days to show use. (Not saying it's accurate), and they can actually have false negatives since there is less blood flow to the area, especially toe nails. It's more chronic, long term use than a short window. 

You probably need to talk to an MRO or someone in that field. 

Nail test will show positive only after a month. Literally takes 3 to 4 weeks for drugs to show up in nail tests. Also, when it drug is deposited into the nailbed from the blood stream, it doesn't simply go to the "bottom of where your nail starts to grow," it ALSO is deposited through the full thickness of the nail which means.....even at the top where your nails are normally clipped, the drug shows up there as well.

Most people think a nail test and the drug starts at the base of the nail near the bottom (cuticles) nd grows "up" to the top. That's false. It starts EVERYWHERE in the nail (even the portion that is closest to the part you clip) and it grows through the full thickness of the nail.