Good thinking!

I live in an apartment building, and the outside water might or might not be working -- plus, there isn't a hose so I have to take a bucket downstairs and bring the wet bike back up on the elevator (because I can never get it completely dry).

To wash the bike indoors, I stick a pan under the bike and dump water on the critical parts. Usually makes a mess, but my floors usually need mopping so it all works out in the end.