But with the global cereal giant stocking hundreds of different brekkie options, what variety does the Queen goes for?
Former royal chef Darren McGrady, who worked for the royal family for more than 10 years, previously revealed that Elizabeth II preferred Special K – and had enjoyed a bowl most days during her 70-year reign.
"Sadly, the Queen is not a foodie. She eats to live, unlike [the now late] Prince Philip who loves to eat and would stand and talk food all day," he told The Telegraph in 2015.
"For breakfast, the Queen likes cereal – usually Special K – and fruit."
He added she also "loved" scrambled eggs with smoked salmon and a grating of truffle, but added she rarely ate them as she was "too frugal to ever order fresh truffles".
"[She] only really enjoyed them at Christmas when the truffles were sent as a gift," he explained.
McGrady was also the chef who revealed in his 2007 book Eating Royally: Recipes and Remembrances from a Palace Kitchen the Queen was a fan of sipping on a dry gin martini every night, a habit she reportedly gave up last year.
She also has a tray of Twinings' English breakfast brought to her room when she wakes up at 7.30 each morning, according to author Brian Hoey, in his book At Home with the Queen.
And if you're wondering, we know you are, she reportedly doesn't take sugar.