We have a whippet, a greyhound and a grumpy old lurcher with attachment issues, and they eat Pets at Home's own brand Lamb dried food mainly, supplemented with occasional meat scraps and whatever else they can reach (which for the Greyhound is most things). They love carrot, and can determine by sound alone when someone is getting the peeler out of the drawer. The lurcher is partial to an apple core and will materialise next to anyone who is eating an apple, then stare intently at them until they give him the remains.
We used to buy whatever was on offer, either Science Diet or James Wellbeloved, but some disagreed with them, others were too small a kibble, and the Lamb one seems to be well liked and generally agreeable to all. Worst we tried was Purina, which gave them all terrible wind...
Skinny dogs do tend to be scavengers (IOW, thieves), and will grab whatever they can find. We were sitting at the table once, when we realised that the Whippet had gone, having slipped through a gate accidentally left open. We found him upstairs, just finishing a bar of 85% cocoa solids chocolate! Later on at the vets, after they had admistered an emetic, the nurse came through and told us that he had brought up the chocolate, then came back a few minutes later to ask if there was a chance he had eaten any sweets? A little later she reported the appearance of sandwich remains! An overnight stay and a charcoal meal or two later and he was fine, but we do keep a closer eye on him now.