If it was oil based paint, sponge turpentine on it. Blot with clean rag to prevent paint from spreading. For water based paint scrape off excess wash in hottest water possible.
Chances are you can't get the stain out. Unless it was textile paint that sets with heat. Any other kind of paint is permanent. Don't throw the sweatshirt away though, find a great applique at your local craft store and put it over the stain. If that looks off-center, add more stuff to the sweatshirt to make it look trendy. You can find all kinds of books in the library on re-making clothes. Also, there are lots of books on making sweatshirts into jackets.
Even if you don't sew, use the iron-on appliques you find and you can add lots of other embellishments by using products such as Steam-a-Seam 2 that permanently bond fabric to fabric. It also will bond appliques that aren't iron-on. One book I saw for non-sewers uses a glue gun to put on the embellishments. It even uses it to keep seams together if you don't have a sewing machine.
In most of the other questions about grease stains, nacho cheese stains, orange stain, salad dressing the answer is the same. I have successfully removed stains using a product that is made to take grease off car mechanics hands. One of the ones I have used is called Go-Jo, but there are lots of others. You find those in the car department at Wal-Mart or Target and you can find them at your local car parts store. I have even found them in the dollar store. I use this product often to get the stains around my husband's shirt collars off. You just rub it in thoroughly and then throw it in the wash with the rest of the laundry. Don't put it on and let it sit, put the article in the washer immediately. There are lots of books about cleaning that mention this product.
Add your voice to the conversation. Click here to answer this question.