How can you make your ankle need surgery after a sprain?

Why do you want that: Your question made it sound like you're think about damaging your ankle to have surgery. You don't want that, unless it's absolutely necessary. You have surgery only if your ankle is unstable, if you've completely disrupted tendons or ligaments. In other words, you get surgery if your ankle isn't stable to support your weight. Better to let it heal and do the rehab. Cycling is good for that.

Improper immobilizin: If you sprained your ankle and didn't immobilize it with an air cast or a walking boot, depending on the level of sprain, you could potentially be looking at a surgery to tightened down tendons due to a now unstable ankle joint. Once you sprain an ankle, whether or not properly treated, you never get 100% back leading to instability and re-occurrence. If you are falling/ tripping, get it looked at.