You can purchase hydrated jelly beadz.  Or if you prefer you can purchase dry jelly beadz and hydrate them yourself.  If you have purchased dry, follow the instructions on the label - add water to the beads and allow to bloom for 6-8 hours.

Fill your water bottle about half full with Orbeez.

Blow up your balloon.  Twist the end of the balloon to prevent the air from escaping.

Lay the bottle on its side.  Keeping the balloon twisted and the air still in the balloon stretch the end of the balloon over the top of the bottle.

Stand the bottle up and untwist the balloon.

Turn the bottle upside down and allow the Orbeez to fill the balloon.

When all of the Orbeez have transferred tie the balloon.  You now have a sort of Yo-Yo filled with Orbeez which is fun to play with.

You can stop with your filled balloon or continue and create the stress ball.  To continue, untie the balloon and slowly let all of the air out.

Press down on the balloon to get as much air out as possible.  Tie the balloon again, as close as you can to the Orbeez.

I usually tie a second knot for safety. You are all done.