I'm going to go out on a limb here and assume we are talking about the windshield washers.

You can use a fine gauge sewing needle to prick out the crusty stuff in the nozzle. I've done it many times before. You don't want to use something that is close to the diameter of the hole, as you will just block the tube behind the nozzle. You want to just scrape at it until you can get it broken up and then use the washer to blow the little bits out as you go.