If you truly love your dog, you will be responsible and take the dog to a vet, where they will administer the proper way of euthanizing it. If you can't ( or won't) do that, then PLEASE, do not EVER own another dog again. All animals have the right to be taken care of properly. And the proper way is to take it to a qualified vet.
Don't even attempt to put your dog to sleep. If you cannot afford to then still take him to the vet or shelter and relinquish ownership. And please don't ever adopt a pet again. You are an animal's worst nightmare.