If you've ever driven a car on a long road trip, you have probably faced the challenge of staying awake while driving. The stakes are high on this one - failure could mean death. I am going to share a tip that has worked better than anything else that I have tried, and which has never once failed me. Who knows? It might save your life.
This is what you do: listen to familiar songs which you can sing by memory and sing along to it - that's it.
It's better to have a collection of these songs ready - possibly a favorite album, because if you listen to the same song over and over again, you might get bored after a while.
A variation of this technique is to try to learn the lyrics to a song which you are pretty familiar with, but haven't gotten the memorization down yet. Listen to this same song on repeat, and try to sing all the syllables along with the track - it's okay if you sing/say the syllables slightly later than the track. If possible, try doing this with multiple different versions of this song - different recording, different style, different arrangement, different artist, etc.
If don't have any science to back up why this works. If you do, please post it in the comments. If you tried this technique, please let me know if it worked for you.