When I was teaching one of the kids asked me if strawberry milk comes from pink cows, and tbh that was one of the more reasonable questions I've been asked during these group nutrition classes.
Here is a quick refresher natural sugars are found in unprocessed fruits, grains, and dairy. These sugars provide the body with long lasting energy.
Added sugars are found in many processed foods such as cakes, cookies, candy, soda, donuts, juices, sauces, dressings, dairy (think danon/Yoplait yogurt, chocolate milk, etc), and pretty much any proccesed sweet.
Added sugar gets absorbed quicker in the body, hence used up quicker. Essentially it may cause you to be hyperactive and suddenly crash. A high added sugar intake for long periods may lead to detrimental side effects like fatigue and chronic disease such as diabetes, heart disease, GI issues, and certain cancer.
Which is why we should limit our intake of added sugar to 6-9 tsp per day. Luckily for you guys the new USDA guidelines require nutrition facts/labels to list added sugars. Another way to make sure you are staying within the guidelines is to eat food as close to the natural form as you can.