Well, yes, it is normal to have dark circles under your eyes after you have eaten sugar. And generally speaking, there are many reasons which can lead to dark circles under eyes, such as lack of sleep, stress, coffee, and others. But on the other hand, you should know that eating too much sugar can lead to dark circles too, for it can keep you awake all the night. And that is jus like coffee. You should pay more attention to it. For your situation, you can just try some ways to treat it. For example, drinking enough water, using some cool teabags is effective. In that way, they relieve your symptoms. Beside, you can eat some black chocolate which are rich in Lutein and zeaxanthin, which can do a good job to your dark circles and the sight. Of course, you should avoid eating too much sugar.