Even small, lazy dogs will appreciate getting treats, but that doesn't mean you have to give them directly to them. Hide some treats around the room when they're not looking and motivate them to get off the couch and hunt.
Just because your dog likes to lay around doesn't mean they can't be productive. Get them some dental chews to give them something a bit more mentally stimulating than just laying around and help them clean their own teeth in the process!
Just because your small dog is lazy doesn't necessarily mean you have to get them exercise all the time. On occasion, indulge both your and their laziness by cuddling up in bed or on the couch and watching some TV. There are even dog TV shows now if they tend to get bored quicker than you do.