Fatigued! How do I stop feeling like this?

I feel extremely fatigued. This is not the same as feeling tired, it’s more of a weird jittery, trembling, weak feeling. Like all of my muscles have turned to jello. It’s quite unpleasant and I’m supposed to be heading out in an hour to meet some friends – how do I snap out of this? Anything I can eat or drink? Exercises? Hold my breath for 30 seconds hanging upside down with a brown paper bag over my head?

This has happened before and usually passes after a while eventually – I just wanted to know if anyone had any tips on expediting the process.