There's no spell I know that's going to allow you to stay awake or give off symptoms that you actually have slept. Sleep is essential for the body for it to rest and reenergize. However, there are certain things you can do to ensure a restful and undisturbed sleep.
Have a small cup of Chamomile Tea. It helps with calming and relaxation.
If you have these herbs, you can fashion an equal amount of Anise Seed and Basil to prevent nightmares and ensure a peaceful sleep. Even with natural things: Make sure your bed is comfortable, you have fluffy pillows, etc.