The numbers game is a simple game to play and can be used all season long.  Whenever the coach calls out a number, the players must get into groups of that number as soon as possible.  Whoever isn't in a group "loses".  For example, if there are 16 players at the training session and the coach calls out "4" the players will quickly get into 4 groups of 4.  However, if the coach calls out 3, they will get into 3 groups of 3's and one person "loses".  When the coach first introduce this game, there might be a "punishment" for the loser, which could be something like 5 star jumps or 5 donkey kicks(can the coach make it soccer related  i.e.. keep ups). Quickly the players learn that whenever they hear a number, they grab whoever is closest to them without regard for whether it's a "friend" or "foe".

This is a great way to get players to work with different team-mates throughout a training session or season.  It even works with larger numbers (if you want to split 16 players into 11 and 5 just yell "11" and those 11 become the first group right away.  If a player wants to be in the group of 11 they will do so and if they don't that is their decision (this is a great way to figure out who wants to do things because the players will frequently figure out what you are thinking with
the numbers and will get into the bigger group quickly to participate.

A coach can and will assign players into the groups but other times yell out the number and let the players do it, which saves time and avoids potential conflicts.