How to get my parents to let me go to a sick party?

As much as it sucks, there's no way to make them let آپ go to the party. It's probably for the best. Even if آپ say آپ won't drink, bad things can still happen. A friend of someone I know did that, and someone slipped something in her drink; and she got raped and she ended up in the hospital for it. It's best آپ don't go to a party like that.

I know the party has most likely been and gone سے طرف کی this time, but I have some ideas for future reference.
Tell your parents that آپ think they have raised آپ to be responsible and mature enough to go out with your دوستوں and not get into any trouble. It's a bit of a mean trick, but either they let آپ go, یا they are forced into admitting they didn't raise آپ well enough. When you're asking them, make sure آپ demonstrate this maturity, and talk to them in a level tone, and don't throw a tantrum if they say no یا get angry. Let them know you're upset that آپ will be missing out, and ask them to reconsider.
It's also important that آپ take into consideration what was کہا in the answer above mine. آپ کہا you're not going to drink, but if آپ go to parties like this, make sure آپ keep yourself and your دوستوں safe. It's great that آپ told your parents that there will be alcohol, because if آپ get in any sort of trouble, they should be the first people آپ call for help (or if it's serious trouble, emergency numbers).