I personally have never over praised or given a treat to a puppy for doing their business outside. And I do tell them "no" when they do it inside. Not a loud NO, just a soft-spoken lower-case no, so they understand it's not okay. Then calmly pick them up and take them out. Just be calm and consistent and they catch on pretty quickly, if not you're giving the puppy too much freedom in the house. If that's the case, just keep them tethered to you for a couple days, so you can mark when they start to go with a no, and calmly take them outside.
It's not the size of the dog in the fight, it's the size of the fight in the dog. Mark Twain