Restroom odors can be defeated! Urine is stubborn stuff, and it will penetrate into grout (even sealed grout and floor finish) and grow odorous bacteria.
First of all, of course, be sure your toilets and urinals are being cleaned by your janitorial service on a regular basis. Toilets and urinals have all kinds of nooks and crannies that can harbor bacteria. Tile grout on floors and walls is great for holding stuff together, but unfortunately it’s also “great” for harboring bacteria because it’s so porous. It needs to be cleaned thoroughly, rinsed well, treated with an “enzyme digester” until the odor is completely gone, and then sealed with a sealer that is urine-resistant.
Usually grout can be cleaned using nothing more than a 50-50 mix of white vinegar and water, or a paste made from baking soda and water, and scrubbed with a stiff bristle brush (old toothbrushes don’t work).
If it’s floor grout, your cleaning service can scrub the floor with a “swing machine” and a bristle brush pad, and then rinsed and wet-vacuumed at least twice.
Whether it’s wall grout or floor grout, have your cleaning service spray on an enzyme digester such as Nilodor® Digester Bacteria Enzyme (about $15 a gallon) while the grout is still wet from cleaning and rinsing. It might take up to a week of applying every day to get the odor under control. After the odor is 100% gone, have them use a urine-resistant grout sealer such as Amrep’s Crystal Guard PS. It won’t change the slip characteristics of the floor, and you won’t even notice it’s been applied after it dries.
General Tips for Grout Cleaning (Hey, some contractors don’t know these things!): Never allow bleach to be used on colored grout, as it will discolor the grout. Metal bristle brushes should not be used, as they will wear away the grout. For everyone’s safety, your contractor should ventilate the restroom when commercial cleaning products are used.