Sources of water?

How do people get, say, 10L of water each day (stored in the car), for drinking and washing?

Gyms? Smuggle containers into the gym, go into the shower, fill them up and smuggle them out?

Public parks, libraries? They have drinking water fountains, but how does one fill a 10L container without looking suss, or taking too long? How does one even fill a container from a water fountain? Use a funnel and hose?

I have a 10L container, but I'm considering buying two 5L containers and using them instead for portability.

Edit: Forgot to mention that I'm in Australia, and we don't have Walmart here, and convenience store don't give free water. No business in Australia gives free water-restaurants give a free cup of water with your meal, if you request for it. And supermarkets don't have taps where you pay and fill up.

Thanks in advance.