I have a 24 ounce bottle.
I drink half of it in 12 swallows during long hikes.
I did a final check last night by polishing it off in 24.
One ounce per swallow.
‘Must be the origin of this useful unit of measure. Maybe I should Google it.
(The photo is the 24 ounce bottle properly dented during a stumble on a Kennedy Trail downhill)