The hole in a Krispy Kreme doughnut is a dual gateway to the Sugar Dimension and the Grease Dimension, bounded by a toroid containment bottle.  It is also a valve, predeterminedly metered to deliver a pound of each respective form of matter in an imperceptibly steady flow when the doughnut is bitten and the gateway is breached.  The virtual containment field remains residual for long enough to sustain itself for a while after the destruction of its physical flour-based matrix.

That's if you eat the entire doughnut within ten minutes.  Luckily, the average duration of consumption is less than that.  Believe it or not, they taste good not just for fun, but by integral design; as a safety measure so failsafe in trial runs that the FDA has waived the usual requirements for visible warnings.

Technically you can eat one Krispy Kreme doughnut and not have to eat at all for the next three days.  (I don't know why the military isn't jumping on this and issuing Krispy Kreme rations.)  And that's why you can gain over a pound for every 4 oz. Krispy Kreme doughnut you eat.  It is not a violation of physical laws after all, merely a clever application of them.

It Uses a Torus Not a Sphere

The problem with a sphere, or any other genus 0 solid, in terms of lines of magnetic force, for instance if you need a containment bottle for plasma or anything else that would melt a normal bottle, like if you're trying for a controlled fusion reaction, is that there's always at least one "bald spot" in the field.  It's like a head, which is roughly a spheroid; the hair has to start at a point and likely bunches up antipodally as well, which in a magnetic field would be a disruption and might as well be a bald spot.  That's not good.  Picture trying to cover a head completely and continuously with hair, without any bald spots or bunchups that would cause a breach of field integrity.

Or you could just trust me.  Can't be done.  It's not like a ball of string either so don't start. 

Now you take a genus 1 solid, like a torus, e.g. innertubes and doughnuts. You can easily coat a torus seamlessly with hair, or lines of force, leaving no bald or bunched spots.  Say you took a stoat, chopped it off behind the forelegs and before the hindlegs, then you take that hairy tube and bend it around so the ends connect.  There it is.  A continuous perfect flow of hair, or a breachless magnetic field that can contain something without physical contact.

As Arthur C. Clarke said, "Any sufficiently advanced technology is indistinguishable from magic."  So... Krispy Kreme doughnuts are... magic.  That's all you really need to know.

But wait till I tell you what I found out about pizza.  Makes the Krispy Kreme trick look like a Pentium 90 with 4 MB of RAM...coming soon.