Well, "Crystal Light" and other such items definitely aren't "whole foods" due to the artificial colors and sweeteners.
Here's the typical ingredient list for Crystal Light:
Citric Acid (Provides Tartness), Maltodextrin (from Corn), Potassium Citrate (Controls Acidity), Natural Flavor, Aspartame (Phenylketonurics: Contains Phenylalanine) (Sweetener), Contains Less than 2% of Artificial Flavor, Magnesium Oxide (Prevents Caking), Acesulfame Potassium (Sweetener), Artificial Color, Red 40, Red 40 Lake, Blue 1.
There's a lot of information out there to consider. Splenda, Nutrasweet, Acesulfame Potassium and the others are all deemed safe by the FDA. Some people feel the FDA isn't a neutral source and has a vested interest in these matters, so think of that what you will. Some people have negative reactions to artificial sweeteners. Some doctors and nutritionists call them "neurotoxins" .
Some people do feel they respond negatively to them, in the form of blood sugar spikes, headaches, muscle pains and other reactions. Also, some believe that they increase cravings of cause other problems by trying to "fool" the taste buds (that the body responds as if a sweet has been eaten).
Some people feel they are a useful and enjoyable dieting tool
Man, how middle of the road can you get, right? Well, you are asking for information, so I am presenting both sides.
You just have to decide for yourself what you think about them.
Again, I personally don't eat them, my partner doesn't eat them and we forbid my child to eat them as well.