If you really really need sandbags to keep water (water, water - not anything else) out. If you are protecting a door, you can use plastic bags partially filled with water. They will mold pretty well to the openings and block water and then they can be backed up with just about anything to hold them in place.
I can't remember where I heard that but it did work many many years ago when Ma Danby worked in the shopping center in San Diego built in the river bed and the SD river flooded up to their back doors. Her manager didn't hink it would work but it did for the brief time needed. We used those bags you pull over hanging clothes, just tied knots in both ends with about 2 quarts of water in them.