I study maths and torii come up a bit, and same goes for physics with tokamak fusion reactors, for instance. In popular science talks, sometimes people say "torus" but most people are familiar with them as "doughnuts" or occaisonally "rings". So I'm wondering, is it just a brilliant coincidence that there is a mainstream "western" food of such value to maths communication?
Apparently Jews eat Sufganiyah during Hannuka, and from my research the spheroidal shape is advantageous as filling can be injected to a higher pressure with less chance of a leakage, such as would occur at corners on something with faces. Ok, I can acquiesce for that, but as far as my (very limited, Australian) doughnut experience goes, there is rarely any filling inside the toroidal doughnuts.
Potential advantages that come to mind is that the hole could've allowed food-stall/vendors to put the doughnuts onto a rack/skewer. Other than that, the only reasonable answers I can think of concern aesthetics, and surface area. A toroidal doughnut has slightly greater surface area than a spheroidal one, and is more compact than a rectangular/linear form, such as that of a churro, but I'm not sure how vital this is.
Do the historians have any insight?
Wikipedia states that Hanson Gregory claims he invented the toroidal doughnut in response to the center of a flatter, spheroidal doughnut not being cooked. Does this explain the popularity? Later the article claims that the "nut" part of "doughnut" was added to the center as it didn't need to be cooked, which feels a little.... contradictory.