Sprinkling water on the grave is not established.

Neither from the Prophet ﷺ nor from the sahaba, may Allah be pleased with them. But those who sprinkle water do so to keep the sand in place so the wind does not blow it away.

This is something specific in our country, for example, sometimes there are strong winds.

Over time, the grave becomes level with the ground.

So they sprinkle water to keep it firm.

The soil, and there is nothing wrong with this. Some also put pebbles.

Pebbles, so that it stays in place, there is nothing wrong with that, insha'Allah the Exalted.

But after a year or two, if someone comes and sprinkles water just to cool the deceased, this is not allowed. This is one of the innovations. Yes, no, this is not allowed.