Sharp "died due to ongoing complications from past stomach surgeries and digestive issues," his official website said.
As a teenager, Sharp suffered from bone cancer that was initially believed to be terminal.
Foster helped Sharp get a recording contract with Asylum Records after doctors told the younger man he had beaten cancer.
"If there is one thing that might be more shocking than hearing a death sentence, it's hearing that death sentence lifted," Sharp wrote in 2006. "Finding your way back into life after being taken out of it for so long is harder than you might imagine."
Sharp's website indicated a memorial service will be held in Nashville, though details were not yet available.