Brew small batches? It may seem like a waste, but its a good way to experiment!
Brew a small(er) batch of high-gravity beer and blend it with kegged, carbonated water in a keg.
Brew a small(er) batch and blend pre-ferment with wine must or cider. Blend post-ferment with existing batch of mead, cider, beer, etc.
Reusing yeast slurry (or sourcing yeast slurry from friends/brewery) reduces water needed to make/chill starter.
On the other end of the spectrum, brew with a friend! Even if you double your batch size, you'll still use less water than if both of you brewed separately.
Maybe stick with regular showers, just be quick about it, eh?