sugar turning to fat? OK THIS IS TRICKY. YES if glycogen stores are full. however, sugar (simple ones found probably in your gum as well) makes you feel fatigued or a little less active after sometime after "insulin" is released by the pancreas to compensate for the sudden surge in blood sugar (so it's probably a good idea to avoid stuff with sugar before you workout). this phenomenon is called sugar shock. also, release of insulin also prevents the liver from releasing fat to be burned as fuel (by triglyceride form which is another reason why you shouldn't eat anything with simple sugars before excercising). in theory, this also applies to simple carbohydrates as it also triggers fast glycogenesis cycles (i think it's called glycogenesis or was it glycolysis? im pretty sure it's glycogenesis) which is leads to manufacture of more glycogen giving an instant full content to glycogen stores and exceeds the said capacity thus triggering again the release of insulin (leading to the blocking again of the catabolism of fat and infact, encourages it). HOWEVER, complex carbs are good (oatmeal) before a workout (not right just before but around an hour or so before) because it gives you a constant steady supply of glycogen without compromising the maximum level of storage capacity of glycogen. why? because the body won't have a chance of storing glycogen. Why? Because of the activity you are doing which is actively depleting the stores of glycogen. why is glycogen good? glycogen is energy. CHECK sports physiology, either from a tortora physiology book or a guyton phyiology book.
IN SHORT
SIMPLE SUGAR/SIMPLE CARBOHYDRATE = very probably and mostly will turn into fat and encourages fat storage further
COMPLEX SUGAR/CARBOHYDRATE = low chance of turning to fat and good source of energy when doing something active. this really helps when you are going to the gym or have an active lifestyle.
about the cookies, if your look in the back of the package of the cookie pack, you should see a nutritional information of how many calories are there in a single serving (i think chips ahoy! considers a serving equivalent to three cookies but i 4got how many calories are there). AS LONG AS you don't exceed the calorie limit for the given day (like me, i have a 1500 calorie budget per day which is hell), you WON'T GET FAT. Eat alot of them in just one sitting, and you are asking for trouble. If you can't resist a cookie, eat one now then another later (like after 2 hours?). This gives your body time to compensate.