There are several websites that suggest vitamin C can help in healing Achilles tendon injuries. Here's 2 of them:
This is a study that suggests that a high-dose vitamin C supplementation once for every 2 days has a stimulating effect on the Achilles tendon healing in rats, yes I said RATS. Further studies are obviously needed.
http://www.ncbi.nlm.nih.gov/pubmed/18309503
On Lance Armstrong's LiveStrong website the question is posed "what vitamins should runners take?" and the list included vitamin C. They also cited "The Rat Study" for tendon healing, lol.
http://www.livestrong.com/article/204240-what-vitamins-should-runners-take/