For years I have been using sandbags for fitness. For larger bags (25 – 60 lbs) I cut the straps off of old backpacks. Here’s how to make a smaller bag, for weights 25 lbs. and under — great for doing Sandbag Burpees, adding a little weight to your Jump Squats, grip strength training, and so on.
If you’re going to use sand, don’t put it straight into the bag! Using contractor-grade trash bags and some zip-ties, and the same technique for making birdseed sachets for a wedding, make some small sandbags to put inside. Cut out squares of plastic, add a scoop of sand, gather up, and zip shut (use pliers to pull shut very tightly). Trim off excess plastic, flatten, and add duct tape to prevent leaks. Pro tip: lots of small sandbags are better than fewer large bags.
Or you can use chain. It’s more expensive, but there’s no muss, no fuss, and you can do other stuff with it — like draping the chain around your shoulders to add more weight during Squats and Pull-ups.
Anyway, here’s the slideshow. Enjoy.