Stretch the opening of the balloon over the end of the funnel. Pour about 1/3 cup of baking soda into the funnel and shake it around a bit until it all falls through the funnel and into the balloon.
Rinse all the baking soda off the funnel, and then use the funnel to pour the vinegar into a water bottle.
Gently stretch the opening of the balloon over the opening of the bottle. Make sure the balloon is draping down at the side to keep the baking soda from falling in.
Lift the balloon so that it is completely upright allowing all of the baking soda to fall into the vinegar.
Watch the magic as your balloon begins to inflate!