Make drill holes around the edge of the bin. Should be small so the balloon knot does not slip through. Make a knot at one end of the balloon and pass a metal washer, pass the end without knot through the hole, stretch it, pass it through the other hole, put another metal washer and make a knot. Make the same process with all the balloons. After 15 balloons you have your umbrella stand ready and functional.
1 metal bin
15 color balloons
30 metal washers (6 mm inside diameter)
Drill or Dremel