This need adult supervision
What we need:
- glass bottle,
- medium boiled egg.
- Boil the egg. It should be well cooked;
- Take several matches; like 6 or 7;
- Light them and as fast as you can place them inside the bottle;
- Immediately put the egg on the bottleneck.
The egg is sucked into the bottle.
Before we place the matches in the bottle, the air inside and outside the bottle were at same pressure and temperature. What we did was light the matches and place them inside the bottle, then fast and quickly we sealed the bottleneck with the boiled egg, this will make the air inside the bottle to expand and heat. After a few moments (depends on the bottle size) the fire extinguish (because all the O2 is finally consumed), the air in the bottle cools and contracts, and now the pressure inside the bottle is lower then the pressure outside, and respecting the laws of physics, pressure outside "pushes" the egg into the bottle.
As an alternative to hard-boiled egg, use a balloon filled like an egg.