I didn't take up coffee drinking until my late-20's. At first I took my coffee black, then I read how caffeine boosts the metabolism. This draws down sugar from the blood. To avoid a cortisol response, it's best to complement the caffeine in coffee with sugar.

This study seems to confirm that fake sugar is harmful. I have family who drink fake-sugar cola products - these don't help their weight. I've seen one person fall apart 'mentally' within 1/2 hour of drinking an electrolyte beverage made with sucralose and other fake sugar.

Ideally glucose is consumed with potassium, to avoid insulin release: milk, orange juice, potatoes, etc... Fructose does not stimulate the release of insulin.