I recommend some soap-on-a-rope.

It looks like the the prior responses were from people owning single family or duplexes,but in bigger buildings it is very uncommon to have hookups in each apartment.but the problems can be several,  one of them, if they put the drain in the sink in scared that the soap etc.

But I won’t get on my soap box about that here.

People either use the t.p. and bath soap that is provided, or they bring their own and what I provided is still in its original packaging. 

A plumber is going to have to pump the pipes with air and spray each joint with soap and water to see if there is air bubbles.

I am not sure why so many who would normally move to evict a tenant are getting on their soap box about this guy.

Wore my worst clothes , had bleach water and soap and had a miserable day .  

It will work for a complete blockage, but to clear the buildup of soap and grease, you need a drain clearing product to break down that mess.Zep has a product called Drain Care.

I'm sure you provide items like towels, soap, linens and the like. 

(Whenever I’m working on a unit, I buy some dawn dishwashing soap to use to was my hands, and paint brushes, jist random needs, and I leave a nearly full bottle for the tenant, and after the cleaners come through they always walk away with it!!)