750 ml, enough to get any man wasted, unlike an eigth/pint which the some of the above people have mistaken to be a fifth, which is about 16 oz which is what youd be seeing people sippingoff of. then theres the good old handle which is 1.75 liters
A one fifth of a gallon bottle of alcohol, or 4/5 of a quart. Previous to the US converting to the metric system, hard liquor was sold in 1/5 gallon bottles. Slightly larger than the current 750ml, but still used to refer to a 750ml of booze