According to what is probably the more widely-adhered-to custom,the beracha of laishaiv baSukah is said only when one eats bread or mezonos in the Sukah.Some say it every time they enter the Sukah after a significant absence.
Ideally, a person should eat mezonos when one is not going to be eating a meal, in order to be able to say theberachah according to all. This holds true also if one is sitting in one’s Sukah and the meal will not be starting for few hours—just tell your wife the Rav said it is ideal to eat cake!
A Sukah has sanctity! And therefore, Mishnah Brurah writes that one should minimize inappropriate levity and frivolity in the Sukah. Imagine the consequences chas veshalom of not behaving properly in a Shul!