Technically this is the small animals forum (hamsters, bunnies) but poodles aren't all that big (assuming it's a toy poodle) so I'll go ahead and answer. :->
The best kind of food for dogs and puppies with low blood sugar will be high in protein, fat and carbohydrate content. Check your dog's temperature if you suspect an episode approaching; he should feel chilled. Try to warm him up, it will help.
I'd consider avoiding any of the glucosamine supplements; there's been some controversy about sugar/diabetes/insulin with glucosamine; it can create problems with your dog's sugar production.
HOWEVER, your dog will NEED some sort of sugar/glucose added to his diet daily. It would be best if the vet gave you a specific supplement geared to your dog's sugar needs.
Otherwise...I'm not clear what your vet meant by a "low sugar episode". Is your dog diabetic? Frankly, it sounds like this may be the case.
I'm going to give you a link to a dbdogdiet site - http://www.bddiabetes.com/us/main.aspx?cat=1&id=389
and suggest you try a different vet.