Thirst

In Serbia people believed that droughts could be caused by the angry thirsty ancestors who didn't receive their water libations..

Serbs, like many other people believed that what the dead miss the most in the other world is water and that they are always thirsty...

Babylonians and Germanic people believed that only those who died in battle would in the other world "always drink fresh water from a well" while everyone else was doomed to suffer eternal thirst

This is why in the ancestral cults it was always one of the most important duties to ensure that the dead have enough water.

Orphic mystery cult promised the followers lots o water in the other world and even gave them a secret formula which would help them to find it.

Muslims in the Balkans used to soak the grave after the burial and sometimes they used to bury their dead in a place hours away from the village if the village was located in a dry area.

In Serbia, on the place where the dead lied at home before burial,  people break the jug of water. A jug of water is also brought to the graveyard and is poured over the grave. At the funeral dinner some water is poured under the table...

In Serbia, for 40 days after the burial, the family of the deceased used to take water from their well to 40 different houses, different house each day, "for the soul"...

In Stip, Macedonia there is a curse  "May no one brings water for him for the other world"...

The belief in the Balkans was that if the dead are not given water, they will drink it from the clouds, and will cause drought. This is why Bosnian Muslims would during droughts throw stones in the air making sure they fall in a river, to bring the thirsty souls down from the clouds.

This is not a Muslim ritual, but a pagan Slavic ritual which Muslim Slavs from Bosnia preserved, with many other pagan beliefs and rituals. I talked about some of them in my post "Alidjun". 

The reason why stones were used in this magic ceremony is because it was believed that stones can tie the souls to themselves. I talked about this in my post "Tombstones".

In Southeastern Serbia people used to place bowls with water in the coffin, cause the dead are particularly thirsty during the 40 days after burial. 

This is a Bronze Age burial cist. Next to the body are two earthen bowls...

Were these bowls, which our Neolithic, Bronze age, Iron Age ancestors placed in graves, also originally full of water?