The term 'doughnut fillers' refers to the various types of creams, jams, and other fillings that are used to fill doughnuts. Creams are a popular type of doughnut filler, consisting of a thick, creamy substance that is usually made from dairy products such as milk, cream, or butter. Creams can also be flavored with various ingredients such as chocolate, vanilla, or fruit. Other types of doughnut fillers include jams, jellies, custards, and even savory fillings like cheese and bacon.