Shooting under some pressure is an essential skill. A player will very rearely get time in the penalty area.
This drill gets them used to shooting quickly while being closed down.

The attacker starts somewhere around the edge of the penalty area. There is a defender, whose starting position is by one of the goalposts, and there is a goalkeeper.

The coach feeds the ball in between the attacker and defender. The attacker tries to attack the ball and get a shot away, while the defender charges out to prevent the shot, or put the attacker under pressure.