I watched a dog who barked too loud for our house and our backyard. Can I watch this dog again?

Why not ask the owner what they do... or ask them if they would mind if you put a muzzle on the dog when it goes out side in the mornings so it doesn't wake the neighbors.. if they say no, then walk the dog someplace else in the morning.

It's hard to stop dogs from barking. They bark because they can't speak :D I do not know why you feel so bad about not watching this dog again, but if you really feel this bad, then just watch the dog again, but do NOT put him in the yard alone, rather take him for a 2 hour early morning walk. He barks because he's unhappy and stressed out and he needs to focus his energy on something else. Give him couple of 2 hr walks/hikes and he should feel better.

Coins in a can sometimes work, and some use spray bottles with water. Bottom line is you cannot leave the dog unattended outside.