Back when I lived in an apartment, the complex had two spaces in the common area parking lot (i.e., not assigned) that was designated as car washing stalls. These had a nearby faucet and a little more space around (like a handicap spot). I used those for washing my bikes. I also had a few friends who lived in houses, and they were kind enough to put up with me bumming water and space to wash my bikes when I need to.