I had one last year. Was utterly terrified, shaking with fear. No sedation at that clinic, just the throat spray.
You know what? It was OK.
The throat spray was very effective, I barely felt a thing swallowing the tube. No pain, no problems breathing at all.
It was uncomfortable during the rest of the procedure, and I could not help retching, but the nurse held me in a gentle, reassuring hug, stroked me and encouraged me. I was lying on my left side. The nurse was behind me.
Removing the tube felt weird, but was quite painless.
The throat spray made my voice a little weak, but I had no problem talking afterwards. It wore off within 30mins and I was able to have a drink.
I burped for hours after! They pump air into your stomach - very strange sensation.
If I have to have another I shall not be afraid. It's no more than unpleasant. It's not painful and does not affect breathing at all.
I hope this reassures you. I'm a dreadful gagger at the dentist, really feel like I can't breathe sometimes. But, truly and honestly, the endoscopy was no more than unpleasant.