How do you say I hope you are spoiled for your birthday in spanish?

It depends on the intent of the statement.

If you mean to say that you hope the person is treated well for their birthday, i.e. receiving a multitude of presents, then "Espero que te consientan por tu cumpleaños."

If you mean to say that you wish that the person shows up to their birthday raggedly or emotionally bereft, then "Espero que llegas a tu cumpleaños completamente podrido(a)."