Suggest Treatment For Wheezy Cough While Having Diabetes Type 2

Hello my husband has diet controlled diabetes type two and also a hacking wheezy cough since a week ago. He has been given via the Dr on the phone antibiotics and is a little better but although robotussin is recommended he felt it did not bring up phlegm and is now taking a Boots one that does have sugar. I am worried as to what might happen if too much sugar enters hismsystem.. He is eating well and plenty of liquids.