I ride stronger in the mid afternoon to evening on a day I've had some calories but not a big meal recently. Hydration hours before is important which is probably a reason I hate riding first thing in the morning. The flatter it is the higher my average power output will be. I ride better when I get lots of sleep.
Example: All of my recent riding has been on Zwift as it's just too hot here in Georgia for me to want to go outside and ride. Last week I had Thursday through Sunday off from work. I rode 239 km last week, which is the most I've ever ridden. I rode hard for 120 minutes on Tuesday, 120 minutes on Thursday, 100 minutes on Friday, 60 minutes on Saturday, and 60 minutes on Sunday. And yet I had my highest average watts on the Saturday ride at 237 watts (FTP is 257 as of a test a month ago). The course was a very flat course with 55 m elevation in 36.1 km.