Why do you think you need to heat the water before adding the sugar?

(Yes, I know it's so it melts but it has something to do with molecules and things I think.)

ig so it's already heated

Sugar dissolves faster in hot water than it does in cold water because hot water has more energy than cold water. When water is heated, the molecules gain energy and, thus, move faster. As they move faster, they come into contact with the sugar more often, causing it to dissolve faster.