Read up on interval training. It may help you. I find it hard to do when I’m riding because it’s best done in a way where the high intensity and rest periods are consistent. You can do it on a bike, but the varying terrain, winds etc. make that tougher. I do intervals on an elliptical at the gym and sometimes on a stationary bike there - where you can program in the length of the segments, and their difficulty/ease. Also leaves me free to enjoy my rides!