So sorry to hear that the doctor was as useful as a chocolate teapot. Sadly, many do not really understand diabetes and also many do not actually listen to their patients. Sweets for high glucose levels? Deary me !!!! Daft advice, probably standard advice for any diabetic.
Assuming that you are diabetic....
The good news is that, if you are a type 2 diabetic, you may be able to get it under good control with a suitable diet and exercise. I can't say about T1 as I have no experience but there are plenty here who can.
The tough bit is finding a 'suitable T2 diet'. Everyone is different, so what is suitable for one person may not be for another.
As a T2 it's the carbohydrates (not just sugars) that are the problem, so getting those reduced in your diet will be important. Just to add to the confusion, people react differently to the same foods, so some quite innocent foods may make your blood glucose levels spike. The only way to discover this is to do blood tests with a blood glucose meter before eating something and then 2 hours after eating that something. Looking for a raise in blood glucose of no more than 2 (ish?).
Myself, I calculate the carbs for every food and meal and restrict myself to less than 130g carbs a day. I eat well too. I also exercise walking every day. I feel well. My blood glucose levels are now within the normal range, however at diagnosis they were about 21 (HbA1c of 140). And, I do not take any diabetic meds.
So, I guess, the first thing you need to do is look at your diet and see where you can reduce the carbs. I think the body does need some carbs so eliminating them completely may be unwise and pretty much impossible.
So, if it is diabetes then....
Sort out diet to reduce the carbs (which means the protein and fats will have to increase to compensate)
Do blood tests before and 2 hours after eating looking for no spikes
Keep a food diary which will show you which foods (if any) give any problems (and avoid or reduce those in the future)
Try not to panic, everyone here will help you when you need it. You are not alone.
Take as much control as you can. Doctors and nurses do not know 'YOU'. Learn as much as you can about diabetes and about 'YOU'. However, if your high glucose and fainting is NOT diabetes related it will be very important to listen to the doctors. I have found that once you get their attention and get them actually listening they are very good.
Let us know how you get on