Drinks in tombs

These are two tombs in Koya-san, with something you may see in many other places in Japan: food and beverages. I guess they pretend them not to be thirsty in the near future… but I do not know the exact reason behind this… I will try to get some more information.
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I guess it’s similar to Mexican culture. They leave Tequila for example.
Probably yes… But what’s the exact reason behind of it? Something about revival, but I am not sure what exactly.