Spanish Noun:Baño, servicios
It all depends which country you are, so will the local words for bathroom be. ‘sanitario’ [sanitary] being the most universal but perhaps too formal. ‘Servicios’ is very much preferred in Spain, but it is rather incomplete, don’t use it in America as most locals will ask ‘¿qué clase de servicios?’ [what kind of services are you looking for?]
Los servicios sanitarios’ would be the whole, but kilometric form. If you are with family or friends you can always use ‘baño’ [bathroom], which can also has the verbal form ‘bañar’ [to bath], used when talking about some thing being covered with a substance, as in “baño de azúcar” [sugar bath] used in cooking recipes.
Example:¿Sabe dónde están el sanitario?
Translation:Do you know where the sanitary is?