A neder is where one forbids oneself benefit from an object such as food.
There's a rule concerning nedarim that says:
וּבִנְדָרִים הַלֵּךְ אַחַר לְשׁוֹן בְּנֵי אָדָם. with regard to vows, follow the colloquial language.
That being so, if one makes a neder not to have hanaah from a sandwich can he eat a hot dog bun? This is based off of the age-old debate of whether a hot dog is a sandwich or not.