Sand or other materials in the water pan besides water work well for heat retention and recovery when you open the lid. What they won't do is control heat spikes from the influx of oxygen when you open the lid. The water pan WILL keep your temp from spiking significantly.
Kamado Joe Big Joe ° Kamado Joe Classic ° Old Country BBQ Pits Brazos Offset
UDS ° Traeger Lil' Texas Elite