I have a sand/water table outside that I fill with water and sometimes add dishsoap for some great bubbles. The children quickly get dirt into the water and it turns into a mud table every time. Sand would be lost completely in a day so I don't bother with the added expense. In the winter it is a snow table so we get use out of it all year round.
But inside? NO WAY! We have a lot of fun inside on bad weather days without that kind of mess!