On Sukkoth we are required to dwell in a Sukkah, which is generally minimally defined as at least eating our meals (which in turn is generally minimally defined as grain-based products) inside the Sukkah. If one was outside of a Sukkah (whether outside unsheltered entirely or inside a building) and ate something that meets the minimum definition of a food that is required to be eaten inside a Sukkah, would that be an activity that falls under the category of a Lo Tha'aseh (prohibition), a Bittul 'Aseh (not actively fulfilling a positive commandment), or an Isur 'Aseh (prohibition due to falling outside the requirements of a positive commandment)?
There is no lav in the Torah against eating outside the Sukkah, so it would just be a bitul aseh. It says "Basukkos teshvu", but does not say anythink like "lo tochal chutz me'suka".
I don't have an explicit answer, but since women are not obligated to sit in the sukkah, and we know that women are obligated to fulfill negative commandments, it would stand to reason that eating out of the Sukkah would be a Bittul Asseh.