My 5 yr old is coughing non stop, what can I give him or do?

Warm water and honey. Mixing about a tablespoon of honey into a glass of warm water can help coat the throat and help suppress coughing a bit. We no longer recommend over the counter cough and cold medicines for children younger than 6 yrs, so natural remedies are best. Keeping the air in the house warm, via humifiers, is also helpful.
Break cycle of cough. I prefer the old standbys of cough drops, menthol gum, popsicles or ice chips. The cycle of coughing becomes so repetative that the nervous system can begin to anticipate the effort & cough without need. Inserting periodic swallowing, (which cannot occur while coughing), breaks the pattern & may allow all involved some peace & quiet.