Sugar dissolution test

Is there a way to detect whether sugar is completely dissolved in a cup of water other than looking at the bottom of the cup?

I was wondering if there is a test or something that can be carried out to determine whether sugar is fully dissolved.

• You could filter it to remove any undissolved sugar. – bon May 26 '15 at 18:38

The sugar will keep dissolving until it reaches it's saturation concentration of around $\pu{900 g/L}$, which is of course horribly sweet, thick and undrinkable as a beverage. Assuming you don't completely saturate the water with sugar in this way, the undissolved sugar will continue to dissolve so long as there is still any remaining in the glass.