I've used Sandbag Training in the past using a cheap duffle bag filled with home made sandbags. I had filled two large heavy duty plastic bags with 25lbs. of sand in each one. I then duct taped them up to keep the bags from breaking. The problem was the inner bags were too large and stiff from the duct tape.
The first homemade sandbag.
Doing 50# Sandbag Turkish Get-ups with the homemade sandbag.
The new outer Sandbag from MuscleDriver USA.
Filling containing bag of sand to put in the inner shell. The zip-loc contains the sand while sewing closed the inner bag. Once inside, the bag will break the first time it is slammed down.