I took my dog outside and he went behind the shed, and when he didn't emerge for a couple of minutes, I went back there to check on him, and I found him eating something out of a bag. So I freaked out and made him come inside and got him to drink water. When I checked what the bag was, it had "METH SEEDS" written on it and it had a brownish powder in it (it resembled brown sugar). I researched meth and apparently its an illegal drug that's really addictive and can cause death. I think my dog has eaten it a couple of times this week because he recently started to smell really really bad (kinda like something rotten mixed with feces) and that's exactly what the meth bag thing smelled like. We just thought he rolled in something dirty so we cleaned him.
This incident happened two hours ago and I have no one to take him to the vet, and right now he's sleeping.
I'm like 99% sure that he's eaten it at least twice before this week, and nothing has happened yet.

I feel soooo irresponsible and horrible and I was wondering what I should do. I have no idea how that bag got in my backyard...

Should I induce vomiting?
When my parents come home, he's going to the vet, but I want to know if he'll be okay until then