best form of vitamin C for collagen production

[frenchmoxie]

What forms of vitamin C do you all use that is optimal for collagen production? Or, is ascorbic acid sufficient? Also, I've got a friend who cannot tolerate citric acid nor malic acid; he also cannot tolerate FRUIT. He is having some issues with tendon/ligament pain and tearing; any suggestions on how he can get more vitamin C in his diet WITHOUT supplementation, and without eating fruit (since he is unable to tolerate)? Thanks in advance!