KK wrote:
Given the water crisis, can I use soapy water, eg. washing-up water, on my
garden, plants, lawn etc.

Thanks

KK

In a word the answer is "Yes". This is what is known as "grey water".
You might want to filter the water through a sieve first though to take
out any large bits of food debris to keep the garden appearance good.
If you don't mind the odd pea or bit of gristle rotting on the garden
though it can act as a bit of mulch!

J.