Green’s Dictionary of Slang

(US milit.) warm breakfast cereals.

1941		S.F. Chronicle 1 June H5/7: The draftees assigned to Camp Claiborne, in Louisiana, got out a glossary of slang terms to describe everyday things in army life [...] The Louisiana lads call [...] hot cereals, ‘North Dakota rice’.
1944		P. Kendall Dict. Service Sl. n.p.: North Dakota rice . . . hot cereal.