A measuring cup or jug. Unless you want a very small quantity in which case a tablespoon, teaspoon. Except that most people who cokok would not - you just use your judgement.
Which unit would you use to measure the water in a full tub?
Gallons
What is the most appropriate instrument to measure
Litres
You would measure the water in a bath tub in gallons.
.
The instrument you would use could be a beaker or a graduated cylinder.
The ceilometer instrument.
A tape measure.
it would be a ruler
Balanced .
if large,pints if small,ounces if medium,cups
cups
barometer
liquid
anemometer
A voltmeter or a multi-meter.