In the later books in The Series of Unfortunate Events, the sugar bowl becomes a cryptic macguffin -- everybody's after it, everybody mentions how important it is, but nobody explains why. There are implications that the sugar bowl would destroy Count Olaf, or exonerate Lemony Snicket, or both.
The plot proceeds, and the sugar bowl is fought over, and at very last it is hidden away in a safe location, albeit under tragic circumstances -- but, very pointedly, we never get to see what is inside.
This is strongly in line with the series' themes of uncertainty, complexity, and never being able to act with complete information. It makes perfect sense that there is no answer; that Handler didn't come up with an answer to "what is the sugar bowl really" because that would be 100% beside the point of the series.
At the same time, Handler builds it up so evocatively, puts such tremendous weight upon it and seems to sprinkle the series with oblique clues and references, that there might be an answer to be found. Even if the books don't actually give us enough information to puzzle it out, there might still be an answer that Handler has come up with, and is, at least, consistent with what we know.
Does an answer exist? Has anyone made a strong, plausible claim to uncovering it? Has Handler gone on the record anywhere, saying there is or isn't a solution?
I'm less interested in what the answer is (although, sure, that too); what I'm interested in is whether an answer exists at all.