Many pet foods are listed as "free from artificial flavours". Actually, artificial flavours are rarely used in pet foods since their natural counterparts (fats, digest, sugars etc.) are both cheap and effective.
Nevertheless, a number of artificial flavours have found their way into the pet food market. Smoke and bacon flavours are fairly popular in some brands of treats and a few foods also incorporate liquid artificial meat flavours. Whether this is to provide a better taste for the dog or a more appealing smell for the owner is questionable.
Synthetic flavours, like many other artificial additives, have been linked to averse reactions in people and animals and since there's really no good reason for their use in pet food, we recommend steering well clear.