In ancient times, and even now, laying food offerings at shrines to gods or other various higher powers was and is a very common practice. But these contributions weren’t always laid out for unseen forces, sometimes they were to honor the dead, or used as a means of mystical protection from supernatural beings.
A common action throughout time was to place food in front of a grave in an effort to pacify or honor the dead. Funeral feasts were where large amounts of food were consumed at a grave site, usually with the recently deceased laying nearby, was a common practice in old times all through Europe. Food offerings were also made at tombs from Greece to Assyria to Egypt.
It has been argued by a few vampire experts that the Egyptian ka (a person‘s soul or life-force) would be forced to leave its tomb and haunt the living if denied its traditional food and drink offerings. And in India there are shrines known as bhadara or bhutastan which are used to provide the bhuta (a ghost/spirit) with a home and constant food, this way the bhuta would have no reason to torment the living.
The offering of food to the dead spread into the world of vampires as well. It was common practice in some areas to lay food or drink at the grave of someone recently deceased in hope that if the person returned as a vampire they would choose to eat the food instead of one of the living.
While most vampires feed on blood, there are a select few that can eat actual food as well. The Bulgarian vampire, the ubour, for example will feed on blood, manure and regular normal food. The vampires Gypsy myths will also pester the living for real food. So while leaving food offerings for the undead may seem like a strange ritual, it is actually something that makes sense in some parts of the world.