I have a small doggy daycare the males keep marking verything. How to I stop it

Since this dealt more with controlling of dogs, I have moved this to dogs, instead of small business

If they are dogs you are looking after there isn't really a lot you can do other than being vigilant and restricting them to certain areas of the house.

It's up to the owners to train their dogs and if you are looking after entire (not neutered) males then the marking is going to be a problem.

I don't know how practical it is but restricting the males to areas that are easy to clean such as rooms with wood or lino surfaces will make life easier. You can buy deterrent products that supposedly stop them from urinating on certain objects or places that you can try as well.

You can also ask the owners if they would allow you to do some training with the dogs.
Some people will be absolutely fine with this, others prefer that they be the only ones to train their dogs.
If they agree then when you see the males marking you can use a water bottle and give them a little spritz and then put them straight outside where they are meant to urinate, or if the owners do not want you punishing the dog (with the water) then just rush them straight outside when they do it.

Male dogs aren't "dirty" and they don't urinate just for the sake of it. The lift their leg on objects to mark their scent as high up as they can, the higher they can get it the less chance smaller dogs have of marking over the top of it.
When they mark the area they are claiming it as their own, something a lot of dogs will do in unfamiliar surroundings or places where other dogs have been.