Why do my hands, knees and (sometimes) feet swell & hurt at night? I'm 24/f/ & a bartender. I don't eat a ton of salt and I drink plenty of water.

Not typical . It is not normal to have bilateral joint swelling on a regular basis. If you only had feet swelling after working a shift you might be able to explain that but not with the knees or hands. A more detailed history, examination and labs are needed to get a better idea of what might be the cause.