There is no reason to give Nuti-cal or Karo Syrup unless you think they are experiencing hypoglycemia. Sugar isn't good for them, but sometimes puppies or dogs under 3 pounds have episodes of hypoglycemia, and need some sugar in their blood fast. You can even cause an episode of hypoglycemia by giving too much Nutr-Cal, so don't use it unless it's needed. When sugar enters the bloodstream, insulin is produced, unless their is sufficient protein to stabilize the insulin, another attack of hypoglycemia will result. Free feeding is the recommended way to eliminate hypoglycemia. See this link for more information:
Hypoglycemia Symptoms and Treatment