For a human to survive we require amounts of glucose which is readily found in sugar. example-when people say their sugar levels are low they tend to be more exhausted and less energetic. this is actually a lack of glucose in the body and can be replaced by ingesting a amount of it. however glucose isn’t only found in sugar but can be found in a variety of foods. so sugar doesn’t give us energy - it’s the glucose within it.
J. Hope this helps you!