One of our customer's contacted us asking for some teacher support. They wanted to know the best way to teach capacity to a child with a working ability of a 5 year old. We offered the following advice:

"Make it visual.  For example put some food dye in water and fill up jugs so they get the concept of different amounts and what a litre or ml would look like.  Or make things with a drink and fill it with 200ml orange juice, 500ml water etc so they have to measure it out."
If you're looking for similar advice, we hope that helps!