Fastest way I found was to get to low water. You can get rid of water supply fast, and the warning comes quickly as well.
Make sure verbal warnings are on in options.
- Start a new game or load an early game.
- Go into inventory (open cardboard box icon on info bar at bottom of screen).
- Scroll down to water and destroy () until you have less than 2 water/person.
- Exit inventory and let game run for a bit. You should get a warning from Veronika pretty quickly.
- Repeat as necessary.