See here where it is a machlokes rishonim if kiddush can apply before Davening, and the halacha as decided by the Shulchan Aruch is like the opinion that it does not.
The Mishna Brurah holds that you do need to make kiddush before davening, but I guess the best way to understand him is that he is being more strict than the Shulchan Aruch in this. In any event, Shulchan Aruch didn't really address eating before davening, as it is normally not allowed.
Those who allow eating before davening, allow it strictly in order to be able to concentrate better during davening. Accordingly, a teacher of mine (Rabbi Avraham Mann) said this would even allow eating bread before davening. It is the custom not to, but in strict halacha, there is no difference.