there are different types of diabetes. Type 2 diabetes is caused by insulin resistance that over time develops into high blood sugar and overt diabetes.
Insulin resistance is caused by being overweight, by inactivity, and by genetics.
The best way to prevent or delay type 2 diabetes is to eat a lower carb diet (avoiding added sugars), which also means avoiding flours and particularly processed foods, and limiting starchy vegetables and fruits. Additional benefit comes from exercise, and of course weight management.
Sir Lindsay Hoyle has been diagnosed with Type 1 Diabetes. This type of diabetes is not caused by insulin resistance, it is caused by lack of insulin. Typically it is an autoimmune disease where the immune system attacks and destroys the pancreas meaning that it is not able to produce enough insulin to keep blood sugars steady. The treatment for type 1 Diabetes is injected insulin. Also controlling the amounts of carbs eaten, exercise, and weight management will be important in helping management.
Do you have a blood glucose meter? It would be very useful to know what your blood glucose is at the time that you are feeling like you need to eat sugar / sweet tea.
Blood glucose meters are freely available at most pharmacies.
You may be experiencing rebound hypoglycemia. So the situation with you taking sugar may be worsening your situation. It works like this; take sugar which causes insulin to rise. If you are insulin resistant then your insulin levels may over shoot and your sugars may drop precipitously, leaving you low and making you feel like you need more sugar.
Suggest that you may want to be eating a high protein low-carb diet, with plenty of healthy fats. This will help get your blood sugar stable. Low carb diet which focuses on reducing carbs, adequate protein (target 1 - 2 g of protein / kg of body weight) and intake of healthy fats (coming with your foods) will surely improve your situation.
Coffee is not the answer, changing your diet will be.
I would suggest that you research low carb / ketogenic diet, paleo diet, or whole foods diet. Though keto may be better for you as it will directly address insulin resistance, and also avoids sugars, starchy veges, and sweet fruits.
The basics of this diet are:-
Eat adequate healthy proteins. This will mostly be meats of all types, fish, eggs, some nuts, unsweetened protein powders can also be used.
Limit carbs: Carbs will come mostly from a wide range non-starchy vegetables and some limited cold weather fruits (such as berries)
Fats should be unprocessed and will mostly come naturally with your quality proteins. Cheese, butter, cream, olive and other cold pressed oil, fat from animal products.
You eat unprocessed and minimally processed foods as close to their original and natural state as possible. ie. Whole foods.
The foods you don't eat are anything with added sugars, anything containing or made from grains, starchy veges particularly corn and potatoes, sweet fruits.
When you eat low / carb or keto you need to make sure you get plenty of electrolytes, like salt, magnesium, potassium, etc. This will avoid "keto flu". Bullion or stock cubes made into a simple broth can be helpful at the beginning.
I do not suggest replacing regular soda or sweetened tea with artificially sweetened beverages. Better that you substitute other things like unsweetened teas, plain water, fruit infused waters, etc. and train your "taste" away from sweet tastes. The first week would be really hard, but I reckon you could adapt pretty well after that time. And once you get your body weaned away from sugar your energy levels should also improve.
Take up exercise. Do you have a pet to walk? Can you borrow one, if that is something you might enjoy. Losing the excess weight will come from changing diet and increasing physical activity. You will feel so much better if you get back to fighting weight... and you greatly reduce your probable insulin resistance.