You're ultimately in control of the situation. If you explicitly tell them that under no circumstances do you want to take a drug to induce sleep, they're not going to force you to. You could just call it off if you can't sleep.

I've taken a sleep study before; they're not that weird, just a pile of sensors and a bed. And I also know from multiple people that if you do have any form of apnea, addressing it can have a life-changing impact.