I don’t know what spadoodios are
It’s a portmanteau of “doodie” (poop) and “Spaghetti-os”.
The Spaghettio-s jingle went “Uh oh, Spaghettios”
Uh Oh Spadoodios
The joke is that he was using the line from an old commercials for
Chef Boy-ar-de Spagetti-os. In ther commercial a kid says “Oh Oh, spagetti-os. Stewie says a variation on that line when he was talking about, doo dy, do do, or poop. Spadoodios