Diabetus is a mis-pronunciation of the word diabetes.
It all started with Wilford Brimley. A spokesman for Liberty Medical.

Any high sugary corn syrup filled products that are commonly consumed

Diabetus is another word you can call "Sugary food".

A mis-pronounced word by an old fat guy on a horse in a stupid commercial that a lot of people make fun of.

yeetis diabetus is a rare desease that makes you die

A way of expressing humour while at the same time making fun of Wilford Brimley, the old guy from the liberty mutual commercials who pronounces diabetes wrong.