thanks for your query,
i have gone through your question, the mettalic taste might be because of the antibiotics and the respiratory tract
infection..one complication of diabetes
is dryness of the mouth secondary to that your taste sensation will change...
once you complete your antibiotic course automatically your taste sensation will become normal,.... keep drinking lot of water, keep sipping the water..if the dryness is too much then you can use artificial salivary stimulants..(wet mouth....its available as gel or liquid...you have to apply it on the mucosal surfaces of the cheek region which increases the salivary secretion...better consult a oral physician for consultation and opinion..
i hope my answer will help you..