Each campervan category has a different set-up & lay-out with different specs & features.
Compare all campervans to see the differences and similarities.
To answer the drink water storage question....
All Self-Contained Campervans come with a sink & tap, which can be found inside the vehicle behind the front seats.
The Dream Sleeper Mini Campervan also comes with a sink & tap, which is part of the fixed kitchen set-up at the back of the campervan.
All remaining campervans come with a portable 10-litre water tank, that can be placed on the cooking area, a picnic table etc to tap water.
See for an overview of the water storage or sink with tap / faucet options for Spaceships campervans in New Zealand, the photos below.