Decimeters or Inches
I would use a measuring jug, not any spoon.
depends on what item you are measuring
With a ruler, or a measuring tape.
a tape measure
a tape measure
If a person wants to measure the water in a small glass, they could use a measuring cup. A person could use a measuring spoon to measure the water.
If you are measuring it's length, a ruler is adequate
I woould use a small measuring spoon, as in the image
If you want to measure the length of a spoon, you'd use centimeters or millimeters. If you want to measure its capacity (how much it could hold), you'd use milliliters.
Units of mass are used to measure mass, not length.
Centimeters/inchesThe most appropriate metric unit for the purpose of measuring the length of a pencil would be centimetres.
Feet and inches