besides drinking coffee, how are you supposed to have energy to 'sound interesting' and keep the listeners paying attention?
Try Monster! Just kidding...
That's a tough one. But I guess you just (the speaker) need to really care about what you present. If you care, you'll at least try to engage your audience because after all you want your audience to get something out of your presentation.
Good point. I try to be well-rested and not have an empty stomach if it's a longer presentation. But yeah, caring about your topic really helps and your energy can be contagious to the listeners.