How to cope with metallic taste during chemotherapy?

Hi there, 

my father has stage 4 terminal bowel cancer. He is receiving palliative chemotherapy and is suffering with not wanting to eat or drink anything due to a horrible metallic taste in his mouth. Could anyone please offer some advice on how I can help him? He is only 61 and it is so awful to see him go off his food and drink which he usually loves! Thank you