You can get vacuum pumps for wine bottles: you use them to seal wine in an opened bottle, to keep it fresh.  Do you have one at home somewhere?

Buy some marshmallows, and cut them into small pieces.  Drop them into a wine bottle, and get busy with the pump.  You may find it quite hard work.

The marshmallows will gradually grow – so gradually, you may not even notice.  But when you let air back into the bottle, they revert to their normal size very quickly and dramatically.

As the air is removed from the bottle, the air trapped inside the marshmallow pieces compensates by expanding.

But it doesn’t mean you get more marshmallow for your money.  And even if you did, they’d be normal size again before you could extract them.

Oh, and by the way, you won’t be able to get them out of the bottle again anyway.  We know.  We tried.