I know that Queen Sofia of Spain has her cooking maids make healthy food for meals everyday, mostly vegetables, salads, fish... though the King doesn't like much that food and appreciates a good pork beef, fried potatos, etc... but can't eat that at home. (I saw that on a TV program)
According to this site:
The Prince of Wales was so fussy about his soft-boiled eggs that his staff would prepare up to seven for him every morning in the hope that at least one would be done to perfection. Charles's private chef during his first marriage, revealed that the prince's security detail would inform the kitchen as soon as HRH was on his way home for tea. "His eggs had to be boiled for exactly four minutes".
QEII favours brown eggs, believing that they taste better. Her great-great grandmother, Queen Victoria, ate her boiled egg, served in a golden egg cup, with a golden spoon.
Queen Victoria, who was convinced that "things taste better in smaller houses", favoured plain food. At home, she favoured pies and invalid soups – pearl barley or potato – washed down with her favourite drink, a mixture of claret and whisky.
The Duke of Edinburgh is said to be obsessed with barbecuing in quiet corners of his wife's estates.
More interesting stories about other British royals in that link.