You will need:

- 4 plastic bottles
- Vinegar
- 3 tablespoons of soda
- 3 balloons
- Liquid food coloring

Cut off the upper part of one plastic bottle, then stretch the balloon over the neck of the removed part. Using it as a funnel, sprinkle a tablespoon of baking soda into the balloon. Carefully remove it, and do the same with the other balloons. Pour some vinegar into the remaining bottles, and add a few drops of food coloring. Now carefully stretch the balloons over each of the bottles’ necks, taking care not to spill the baking soda inside them. Then just lift up the balloons with your hands so that the baking soda drops down into the vinegar. The soda will react with the vinegar, and the balloons will inflate by themselves.