The Fartlek (Swedish for "Speed Play") Training method is a great fitness tool that is excellent for soccer specific conditioning. It is less monotonous than the typical interval training and can be easily customized to focus on the needs of the team. It only requires 20 to 30 minutes including warmup and cooldown where the player trains at varying speeds and intensities. Below you will find a Fartlek Training session that would be suitable for soccer.
You can also mix in any number of the following activities: