How do you ensure not to fall asleep when meditating first thing in the morning after waking up?

You don't meditate first thing in the morning waking up. Meditation needs a relaxed but alert attitude and posture. I recommend waking up, showering, having a healthy breakfast and then meditating with alertness and starting your day. Sleepiness is common but if you feel sleepy, you should take few deep breaths, really deep breaths and focus again.