Navel oranges are known for being very sweet, yet not too acidic in taste, and a good choice for using in cakes as they also peel very easily and do not have seeds. Should you not find navel oranges, then mandarins, which are small and sweet, or Cara Cara oranges, which are sweet like navel but have a hint of red, are excellent choices too, however, all types of sweet oranges will work well.