It is always best to test your fabric with the following solutions before using them on your garment. Some dyes will resist discharge. Not all dyes will lighten to the same color.
Bleach is the most common color removing agent. It works best on cellulose-based fabrics like cotton and linen.
To fade a garment, try mixing some bleach into a plastic bucket of water and leaving the t-shirt immersed, watching it carefully until the desired shade is achieved. Remember that a wet t-shirt is always a couple shades darker than a dry t-shirt.
Make a 25/75 mix of bleach and water and try painting the solution onto areas of your garment you want to fade slightly. Use a hair dryer on your recently painted areas to see the final result. Apply more solution for more fade.
Use the bleach straight out of the bottle to create bleach stains, which could help show that the garment has been around for a while.
For a thickened bleach solution, try dishwasher detergent with bleach, or add a thickening agent like Monagum.
For a powdered form, try Ajax cleanser or similar products.
Although a good rinse will usually stop the bleach from lightening or destroying your garment anymore, you can try a product like Anti-Chlor to neutralize it completely, if there is a concern. You can also use Bleach Stop, or even hydrogen peroxide.
Hydrogen peroxide will not remove most dyes, but it may remove some of the dye – and you’ll get a less severe and less damaging result.
Rit Color Remover, Tintex Color Remover, Carbona Color Run Remover
Thiox, Spectralite, Jacquard Color Remover, and Dharma Dyehouse Color Remover
Rit Fast Fade for Jeans, Dylon Easy Bleach, pool disinfectant
Jacquard Discharge Paste
Put your garment on a mannequin and leave it out in the sun for a couple of months, positioning the mannequin every couple of weeks to achieve a realistic fade.