If the syrup didn't perk him up then it is probably not hypoglycemia. You should still feed small meals to prevent it from occuring.
There are a couple of other things that may cause similiar symptoms. One is from vestibular disease. Symptoms include standing with legs spread out, swaying, head tilt, abnormal eye movement, walking sideways, falling over and may include vomiting. There are a few things that can cause this condition such as an ear infection, some medications and old age. Have your Vet check your dog for this condition.
Here is a great site on this:
Another condition seen in small toy breeds is a liver shunt which is usually a genetic condition. It is a condition where instead of the blood going through the liver and being cleansed, part of the blood is diverted around the liver resulting in a toxic buildup in the blood. You can read about these here. http://www.malteseonly.com/shunt2.html
If it is possible that your dog ate something toxic such as chocolate, cocoa mulch, antifreeze, medications then he will need to see a vet immediately.
Here are some signs that would signal that you need to get him to the vet ASAP:
if your dog becomes dehydrated. You can tell by pulling up the skin between your dog's shoulder blades and seeing if it flows back down normally. If it stays tented or is slow to return to normal, your dog is dehydrated and needs fluids immediately and should see a vet as soon as possible.
If your dog's gums and tongue become pale and not their normal pink color.
If your dog's rectal temperature is over 103F (101-102.5F is normal)
If your dog becomes lethargic and non-responsive.
I hope you find this information helpful.