This problem is useful for young pupils to start considering capacity. It will encourage discussion between pupils and between pupil and teacher.
Possible approach
Although some discussion could be had by looking at the bottles pictured here, it would be good for the pupils to have a variety of bottles/jars for them to talk about and to explore the capacities practically.
Teachers could give the pupils a long time to both discuss their opinions of how the capacities compare and then how they could explore the capacities further. When it comes to finding a "small container", give them opportunities to try out the different suggestions they have.
Key questions
Tell me about your ideas.
Why do you think this will be the largest/smallest?
Why have you chosen this "small container"?
Andrew decorated 20 biscuits to take to a party. He lined them up and put icing on every second biscuit and different decorations on other biscuits. How many biscuits weren't decorated?