He does this by filling a bottle with water and, while holding the bottle underwater, displaces the water inside it with intestinal gas. The bottle should be capped quickly, then labeled with the born-on date and any other pertinant data.
This technique was invented by Eichler Stench in Castro Valley, California, in the mid-1950s. He had an amazing collection of bottles well into his forties. He often carried a bottle or two to fend off Pachuco boys who wanted to beat him up. When faced with a bottle of July 17, 1958, even the most vile and greasy-haired Pachuco would turn and run.
Eichler Stench was last seen in Pacific Palisades, California.