Washing the hoodie in hot water and drying it at a high heat is the best way to shrink it. That said, some types of fabric are resistant to shrinkage, especially those that are prewashed.
If a hoodie is too big for the person wearing it, a hot water wash and high-heat dry may shrink it enough to fit. This only holds true if the hoodie is made from 100 percent cotton and has not been preshrunk. Sometimes, linen and wool may shrink as well. If the hoodie is made from polyester or a polyester-blend fabric, it is not likely that shrinkage will occur no matter what the procedure.
If the hot water wash in a washing machine does not work, another solution may be immersing the hoodie in a pot of boiling water. First, a large pot of water, big enough for the hoodie, is set to boil on top of the stove. Once the water has reached a rolling boil, remove the pot from the stove. The person doing the shrinkage should then carefully immerse the hoodie into the hot water. The general rule of thumb is to leave the hoodie in for approximately 5 minutes, but depending on the size and material, it may have to be longer. Dry on high heat in the dryer.