Casportpony and others are much better with info about crop issues, but water for flushing the crop, and probiotics and antifungal drugs can be used to treat them. Colace or stool softener capsules can be used to treat impacted crop. Here are some good threads and articles to help you decide what is best to treat you hen with the crop problem:
http://www.the-chicken-chick.com/2012/04/answers-from-chicken-vet-on-impacted.html
http://www.tillysnest.com/2012/01/crop-issues.html
http://www.chickenvet.co.uk/health-and-common-diseases/digestive-problems/index.aspx
https://www.backyardchickens.com/t/1053469/impacted-crop-help
https://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
http://www.the-chicken-chick.com/2012/04/answers-from-chicken-vet-on-impacted.html
http://www.tillysnest.com/2012/01/crop-issues.html
http://www.chickenvet.co.uk/health-and-common-diseases/digestive-problems/index.aspx
https://www.backyardchickens.com/t/1053469/impacted-crop-help
https://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments