A solution refers to a mixture where at least one solute is dissolved in a solvent. In this case, sugar is the solute (it is the thing that you are dissolving), and water is the solvent.

A good rule-of-thumb: whichever component has the same physical state as the final mixture is the solvent. Before mixing, sugar is solid and water is liquid. After mixing them, the solution is a liquid made up of sugar and water. So even if you had more sugar than water, sugar is still considered the solute. Fun fact: according to the CRC Handbook of Chemistry and Physics, at room temperature, it is possible to dissolve 2.04 kilograms of sucrose (sugar) in just 1 kilogram of water!

And a caveat to that rule-of-thumb: If you have a solution where both components are liquids (for example, a mixture of alcohol and water), then the solvent would be the one present in a greater quantity.