Split the players up into two groups for a relay type exercise which starts with one player from group 1 running with a ball to the goal on the half way line, trying to score a goal.
As soon as player 1 has had a shot at goal a player from group 2 runs with a ball to the other goal to try to score a goal.
The player that had the first shot (player 1) has to try and defend against the player from group 2. When this player scores or loses the ball to the defender the next player starts from group 1 and the player that has just taken the shot becomes the new defender.
The player that had the first shot and then defended (player 1) goes to the back of theirre queue.
Players should always finish in the same queue and attack the same goal.
Play this practice non stop for about 5 minutes
Check that attackers do not start to run too early each time, giving the defenders no chance to recover after their shot at goal.