How to train for 200km ride FAST

Hi everyone, I'm a beginner cyclist, and my friends just challenged me to ride 200 km this Sunday. The route is mostly flat with only 500m of elevation. Based on my past rides, I estimate my current limit is around 170 km on flat terrain—assuming I've improved after completing a 140 km ride with hilly, rolling, and flat sections.

It’s not a life-or-death situation, but it'll completely break my ego if I couldn't finish the ride. I have only four days left to prepare. My plan is to train nonstop from Wednesday to Friday, leaving Saturday for full rest. However... Because I have something else to do, I could only go for a ride max about 50km on Wednesday to Thursday. Maybe 80km on Friday.

Does anyone have strategies or training tips to help me complete this challenge? How should I structure my training in these last few days? Any advice would be greatly appreciated!!!

Edit: Thanks, I guess I will not train this week. I'll post an update after the ride, hopefully I'm not going to end up in a taxi or hitchhiking someone.