Sue,
the reason you were told to take a sweet drink and to take insulin is that the body needs insulin. If you gave insulin without some sort of carb then you might become hypo.
One of the functions of insulin is to control the breakdown of fat in the fat cells. No insulin and fat cells would break leading to ketones. If the lack of insulin continued, the fat breakdown would continue and these ketones would rise leading to acidic blood ie diabetic ketoacidosis (DKA), a life threatening condition. (it often happens pre diagnosis)
If you are sick, eating nothing and don't take any insulin it is even possible to develop DKA with relatively normal glucose levels.
One of the 'folk' remedies that is supposed to work when you are vomitting is to drink flat cocacola +appropriate insulin. (I've never quite worked out why someone who has D is likely to have a stock of full sugar coca cola on hand!