Bernie's Costume

I've always thought that the scene in which Bernie was murdered was one of the best comedy deaths in movie history. But, after re-watching the movie a few days ago I began to think wonder what the drug was that Paulie injected Bernie with. I know its weird but I think its rather interesting. What could make a man die so quickly and painlessly? I look forward to reading your thoughts.

I am also remaking this movie with my friends just for fun. Its basically just going to be a way for us to kill an afternoon while being in the Hamptons. I am playing Bernie and was wondering if anyone had any suggestions on what my costume should be. Should it be something like a suit or a sweatsuit.