Please....please....please take him to your nearest vet. While I understand that you may be worried since illegal drugs was in use vets are not police and they have no interest in what your roomies are doing. All they want to do is save your dogs life.
I can not tell you how many times we have lost a dog because someone held back about what the dog had really gotten into. We have never reported anyone and few vets do as if word gets out that vets will turn you in more lives will be lost!! You need to be honest get him to the vet and let them know what he ingested. If you are concerned tell them you went to a park and he found it there.
Your dog needs to be treated and the poison deactivated with charcoal or a pump of the stomach contents to save his life.
Do not give him anything else.....wrap him up and get him to your nearest vet asap.
Is there any other vets anywhere near you perhaps another town?
How long ago do you believe he ingested the meth?
OK, Here's what I need you to do,
Make some burnt toast and force your your boy to eat it. Try to get at least two slices in him. Keep up with the water and keep him warm.
I don not know what time it is there, but start calling every vet in the phone book for treatment. Most offices open up at around 9am so if you are close to this time start preparing to leave.
Make no mention of the meth when you call. Let them know you believe he has ingested some type of poison and get him in. Once you are in the office let them know that he may have ingested meth while at the park (Or where ever).
Please keep me updated i will be here for a while today and if I go off i will have one of our other experts keep a eye on this situation.
Your very welcome and if you need anything please let us know.