The basketballs will be rolled back and forth as quick as the players can go.
If one of the players fumbles the ball or does not go quick enough and ends up with 2 basketballs. That player will have to do a push up.
After the push up the game will continue.
Players may not deliberately give their partner a bad feed - if they do then they will have to do a push up.
Rebounding is the least glamorous thing in basketball and one of the most decisive. It is also almost entirely a habit, which means it is entirely coachable.
Good spacing is only the start. The best modern offences teach players to attack the defence's rotations and play in a permanent 4-on-3 - here is how to coach that read.
The ball screen produces almost half of all professional offensive possessions, yet most teams still teach it as a memorised play. The modern approach trains the read - giving players a framework to decide based on what the defence does, not what the coach called.