sand versus shot in speaker stands

Kitty litter works too.

You can get clean dry sand from most hardware stores in a day or two. Just ask for a bag of Playground sand. I think it was 70lb at least 50lb and very inexpensive

Find a store near you that sells sand blasting shot. Make sure that is the silica sand type. It is dry and will not clump. I bought a 50# bag at a local tractor supply store for $8. It is more than heavy enough and does a good job dampening resonance.

sonically, lead is best. I have two sets of Chicago stands, spiked on the bottom and top and they work fine. Lead can be safely handled and on the Chicago stands it was easy to seal the tops so no dust could escape.

Lead (~11g/cc) is approximately seven times more dense than dry sand ((~1.6g/cc) or similar materials. Unhappily it is not environment friendly and its poisonous.
Mass is important for speaker stands and affects mainly low frequencies performance - the heavier your stand, the less it will move. Damping it will eliminate resonances that will affect mid and high frequencies and I remember reading advice from a speaker manufacturer that you should mix both to get the optimum filling, as thin sand is much more dissipative than lead.
Some years ago, as I did not want to use lead, I have used a filling of iron small parts (~7.8g/cc) and sand in my speaker stands.
But if an audiophile is really concerned with bass and ecology he can mix sand with gold (19.3g/cc) or uranium (19g/cc) to fill his stands!