Buy him the food.. dont give him any money..and i know its worrying. My mum does as well. Have you sat him down and talked to him about it?.. maybe sit him down and if he wants to stop try and come up.with a plan of action to help him.
If he wants to.. he needs give up alcohol as this is a big trigger to get coke. He needs to delete all dealers numbers, friends who have coke, family who have coke. Delete all social media.. avoid anything and anywere to do with coke. Its hard dont get me wrong. But admitting you have a problem and wanting help is a big stepping stone towards stopping.