The cereal references cocaine, in that the name is a slang word for the drug, the cereal is consumed by snorting it up the nose, it resembles a white powder, and the side effects (nosebleeds, addiction and an inflated ego) resemble some side effects of cocaine. The packaging states the product is "Not to be taken orally".
The cereal is apparently still sold in Grand Theft Auto IV, as it is advertised on the Biglogs website and on small posters around the city, it also appears in some safehouses in Grand Theft Auto V, including Trevor's Trailer.
It was featured in the Liberty Tree article, RAILS Breakfast Cereal Under FDA Scrutiny, written by Beverly Clamhopper, which discussed how the controversy over the side effects had led to an FDA probe and a recall.
There is ambiguity or continuity issues over which company manufactures the cereal: the packaging mentions Biglogs Corp., the GTA Liberty City Stories website mentions Colombian Breakfast Inc, and the Liberty Tree article mentions Mendez Foodstuffs of Medellin.