Just sorcery can be a cheesy answer, but just sleight of hand seems to kill a lot of the effect. If someone showed me something amazing, something that lingered in my thoughts for a while, it'd destroy it for me if they said, "Eh, just sleight of hand. I'm good with cards." Personal opinion here, but that seems to just eliminate the mystery and half-solve what's going on. I may not know exactly how you did it, but I know some tricky stuff was involved.
But, spectators already know it's sleight of hand, right? They don't want to believe. I often wonder about that... when a spec. sees an impoosible effect, they always ask how it's done. We've ALL heard, "How'd you do that?" I'm wondering if "sleight-of-hand" isn't an acceptable answer in most peoples' imagination - some little spark of them that wants to believe they just witnessed something paranormal. It could just be plain ol' curiosity, but still... rarely do you hear spectators launch into a thesis of, "I know you had a special contraption or moved it when I wasn't looking, I just can't figure out when!" You're usually greeted (if the effect was good enough) with pure awe and intense puzzlement, but not analysis.
The supernatural angle can work. Look at psychics with a firm grasp of cold reading and a working knowledge of metal bending. They can get some people to believe. Not always, and not everyone, but it does happen. Some people believe in UFOs - a lot do, actually. There's people who say Bigfoot is real, or that sea monsters inhabit lakes, or that vampires really do exist. Then there's the far out crowd, those that think our government is overrun by a race of genetically-superior super lizards, or whatever. Given the right evidence and presentation, people CAN believe in stuff like that (when I first saw David Blaine's Street Magic special, pre-magician, I didn't know what to think. Did I think magic was the cause? Some supernatural power? Not really, but... jeez, how else did he do all that? What REALLY happened here?)Maybe the 1600's left a lasting imprint. It's certainly fun to think about the otherworldly, sometimes.
I've actually been toying with a weird idea - not so much that I have magical powers, but that I have the ability to change and enforce paradigms on people. That's the presentational hook I'm working on. I don't use powers to push the coin through the bottle, I temporarily change how the laws of reality work and how the spectator sees it. I change the paradigm, there. It becomes a perception and philisophical thing, then - but it's lacking flash, and I want to tinker with it somemore.