[Lordzy]

You could create variables and do those, just like an Admin system.

pawn Код:

new team1[MAX_PLAYERS];
new team1str[MAX_PLAYERS][128]; //To set the name of the team so it's a str var too. We can use other ways too but this is bit easy.

public OnPlayerSpawn(playerid)
{
  team1[playerid] = 1;
  team1str[playerid] = "EXAMPLE";
  return 1;
}

public OnPlayerDisconnect(playerid, reason)
{
 new Lname[MAX_PLAYER_NAME];
 GetPlayerName(playerid, Lname, sizeof(Lname));
 new str[128];
 format(str, sizeof(str), "%s has left the team server. (Team ID:%d | Team name:%s)", Lname, team1[playerid], team1str[playerid]);
 SendClientMessageToAll(0xFF0000, str);
 return 1;
}

I believe it will output like this:
Lordz has left the team server. (Team ID:1 | Team name:EXAMPLE)