Get 2 jugs of premium milk (in this area, it's Mayfield, but what I want is the jugs, not the milk) that comes in heavier jugs.
Get a bag of filter sand. (or really, any dry sand)
Fill the jugs with sand (using a funnel, after you drink the milk, and rinse the jugs)
Add a cup of water with a tablespoon of bleach to the jugs.
Cap the jugs and time them to the ladder
Don't worry about cement or sealing the lids, unless your kids will fiddle with them.