I have one cup first thing in the morning to get my day started off faster. Nothing else throughout the rest of the day. I find it helps wake me up faster in the morning. If I have caffeine to late it's hard for me to sleep.
Sugar is really bad for losing weight. Fruit juice is mostly sugar. You won't lose any weight if you consume a lot of sugar. Stay await from fruit juices. They don't have the fiber you get in fruit.
I disagree that they go one then the other. I think the lower level needs "burn" more when they are not met, but I think you work on fulfilling multiple levels at the same time.