Kool-Aid has been around for over 80 years and it has been staining kids' clothing the entire time. The worst offender, stain-wise, is the infamous cherry flavor, but strawberry, raspberry, fruit punch and anything else red in color is also hard to clean. While some Kool-Aid stains never come out completely, others may with a little persistence and a whole lot of cleaning products.
Run cold water over the stain as soon as you can. It is best if you can do this from the back of the garment so the Kool-Aid is pushed out of the fabric rather than further in. Scrub at the back of the fabric with an old toothbrush.
Rub a solid (stick form) stain remover over the stain if you are not able to launder it right away. When you are ready to launder the garment, first soak the stained area in a pre-wash spray for several hours.
Wash the Kool-Aid-stained item in cold water. Check to see if the stain is gone before drying the garment. If it is still stained, do not put it in the dryer.
Sponge the remaining stain with white vinegar. If the sponging does not remove the stain, let the stained area soak in the vinegar for several hours or overnight before repeating Step 3.
If the stain persists after using white vinegar, soak the stained area in a solution of a couple of tablespoons of baking soda dissolved in water. If you have denture cleaning tablets on hand, you may use several of these instead of the baking soda. Repeat Step 3.
If the stain persists after using baking soda, make a paste of a little powdered all-fabric bleach and water and rub this mixture over the stained area. Let it sit for a few hours, then soak it in a sinkful with about half a cup of powdered bleach. Rinse, and repeat Step 3.