Covering the sandpit when it’s not in use would be my suggestion.

Some kind of cover would work, as already mentioned a few times below. Nothing worse then digging up a cat poo while playing in the sandpit

put a cover on it. Even preschools do this.

I use a cover for my kids sand pit on that is easy for them to take off and on but also so that dog and cat cannot get into it.

Get a sturdy cover – wooden boxes with a pull over cover work well but you have to remember to put it back on after play.
You could also fence it – I have lazy cats and as long as they can see through they won’t jump short barriers

I bought one from tiys r us that has a plastic lid that you pop over it, otherwise a tarp with clips over the side

I made a cover for ours

We have a fitted, blue plastic cover on ours. I saw a great idea the other day – a kids tent with sand in the base. Shady and you can zip it up when not in use!

When it’s not in use, we have a cover that slips over it

I think im going to make a cover

Put a cover on at all times when not in use. Also cats don’t like pepper so could sprinkle pepper around edge just before it and it may deter them!

If you already have one and can’t move it than you need to cover after use or if yours is moveable than consider buying a small tent and placing sandpit in it — 1/ you just zip it up after use and 2/ it provides sun shelter

get a shell pool thing that you can close up at night

We just cover the sand with a bit of shade cloth after the kids have finished playing. Seems to be doing the trick so far. My dogs would avoid the sandpit anyway, but we have lots of neighbours with cats which wander around at night…

my husband built a frame that he covered with shade cloth that sat over the top of the sandpit.