There is no guarantee to be able to unshrink cloth that have already been shrunk. Here are some suggestions that may work.
Some types of clothing are easier to unshrink than others.
Wool is easier than most items to unshrink:
Put the wool garment into a sink filled with warm water.
Keep the wool in the sink for 10 minutes.
Take the garment out of the water and squeeze out all the extra water.
Dry the garment on a towel.
Stretch and pull the garment back to it original size and shape.
Here is another way to unshrink some kinds of cloths:
Put 2-3 tablespoons of hair conditioner into a bucket or sink containing room temperature water.
Soak for 5 minutes.
Lay the garment on a dry towel, now try to carefully stretch the fibers and reshape the garment before it dries.
Dissolve an ounce of borax into a few tablespoons of hot water.
Pour the solution into a sink or bucket full of warm water.
Soak the garment in the borax/water solution for a minute while trying to reshape it.
Rinse the garment in another bucket or sink filled with warm water and two tablespoons of vinegar.