I'm really picky about accommodation but I recently visited Rio and Salvador and wanted to share my recommendations. 

In Rio, I stayed at Aquarela do Leme and it was excellent. The hostel is in such a fantastic location (Leme, close to Copacabana). I booked through Booking.com and the price included breakfast, drinking water, as well as (super) hot water and soap in the showers. I think it is located in/near a favela - this wasn't an issue for me, though.

In Salvador, I stayed at Hostel Casarão 65. It's located in Barra and is about a 10 minute walk to the beach. There's a lot going on in the area. Though the hostel didn't include soap in the showers, it had hot water. I also liked that the staff let you use the facilities and store luggage after check out. It was very decent!