The capacity of a barrel is a measure of volume. The SI unit for volume is the cubic metre. A barrel with a volume of one cubic metre would a big barrel. It could be better to measure it in thousandths oh a cubic metre, a thousandth of a cubic metre is called a litre.
Milliliters is the metric unit to use for the capacity of a thimble.
can of applesause in capacity masurement
Liters would be the metric measurement for volume of liquid.
It would be millimetres.
By capacity, I assume you mean volume. That would be the liter.
You would use millimeters for the measure of the capacity of a paper cup.
Liters would be easiest to use.
Milliliters or ounces.
Probably none because a stream does not have a capacity but a rate of flow.
The unit will be the mililitre (mL).