Sugar; It truly is "the enemy". In many cases, it is worse than consuming access amounts of fats and protein. Sure, we've been educated to this point that eating significant amounts of fats is bad, which is also true, but one can't ignore the negative impact sugar (artificial sweeteners specifically), does to you in the long run. Yet as a society continue to allow it and say it's "ok" to eat, and eating a lot of it we are.
Eating foods that have high levels of processed sugar or "natural, high fructose corn syrup" will likely lead to weight gain, higher blood sugar issues and an increased chance of developing heart disease and other issues related to it. For these few reasons alone, its imperative to be conscious of your daily sugar intake, educate yourself in better options other than sugar, and of course engage in physical activity and movement to utilize what I consider an "energy source".
Sugar-sweetened items such as soda, juices, sweet tea and candy are loaded with processed sugar in the form of fructose and/or simple sugars. This will likely result in an increase of appetite and likely result in a significant storage of glycogen, which when not used will result in fat storage. regulating this scenario with consuming complex carbohydrates (ex. oatmeal, sweet potatoes, quinoa, spinach,etc) is ideal to get a better source of glucose (stored energy) which the body will essentially use for exercise and other daily activities.
With my clients, I usually use "The 10 rule". Anything 10g or less of carbohydrate, you're fine. Of course, I'd rather one get their energy source from more complex and natural sources of sugar (i.e. brown sugar, fructose from fruit, etc), but anything higher than 10g in one sitting and you're at risk of storing this sugar rather than using it (this will be in respect to your current activity levels.