Cornflakes

Cornflakes were a breakfast cereal that Luke Smith included in an early attempt at a joke in the 2000s: "I am so hungry, I could murder a bowl of cornflakes; does that make me a cereal killer?" He was bemused when Maria Jackson didn't find it funny. (TV: Warriors of Kudlak)

Jackie Tyler had a box of cornflakes, among other cereals, in her kitchen in 48 Bucknall House in 2007. (TV: Love & Monsters)

On the morning of her family's visit to her father's grave, Tanya Adeola was eating cornflakes. (TV: Nightvisiting)

Other realities
In Earth-33⅓, a box of cornflakes was among the items an oblivious housekeeper dumped into a Dalek, which she mistook for a rubbish bin. (COMIC: Dalek Invasion - Salford 1987)