Adult supervision is required. This experiment involves flames. Drop 3 matches into the milk bottle First of all place the egg on top of the bottle to show your audience that it will not fit through the hole. Then light three matches, get them burning Take the egg out from the top of the bottle and drop the matches into the bottle - put the egg back on the top of the bottle. The egg will start to go into the bottle.
Heated air expands so the hot air had slightly greater pressure than the air outside the bottle.
When this happened the air in the bottle had slightly lower pressure than the air outside the bottle. This may seem a bit weird, but the air outside the bottle pushed the egg into the bottle. There was no sucking going on, only pushing by the atmosphere.