G.I.
If it is white, which some are, try putting it through the wash with a little bleach in it. If it is a colored one, try oxi clean or something similar when you wash it (clorox has a similar product). I have had great luck with it getting out most stains on colored clothes (didn't get out pasta sauce so far). I also like it because it can be used if someone has bad reactions to bleach as it isn't really a bleach product.