Here is a video clip of me doing a sandbag race for time.  My goal is to get a 50lb, 80lb, and 100lb sand bag down the 30 yard lane in the shortest time possible.  When I filmed this, I used the race as a GPP (general physical preparedness) finisher at the end of my workout.  This type of circuit can be used as a stand alone workout as well. If you do that, I would suggest increasing the amount of rounds you do, maybe 3-5 rounds based on your conditioning level or the conditioning level you are trying to get your athletes to achieve. I would also determine the distance that you are carrying the bags and your work to rest ratio based on the sport that you play.  For example, if I were using this finisher for basketball players, I would have them carry the bags the length of the entire court.  I would also let them rest no longer than a minute and a half between rounds since that is probably the longest amount of time that they will have to rest on the court during an actual game.  By doing this, you are making the race more specific to your sport.

To increase competitiveness, you can definitely make this a relay race by dividing your team up into groups and having half the group on either endline.  Once one player has moved all three bags the length of the court, the player on the other end brings them back to their original starting point and so on.  You can also create variations of this race by designating what type of carry the athlete must do while sprinting.  For example, the first bag has to be an overhead carry, the second bag has to be a zercher carry, and the third bag a bearhug carry.  By doing this, you are forcing the athletes to work different muscles each time they are carrying a bag.  Whether you go individually or as a team, chart their times and post them so that they know what times to shoot for the next time they do this type of race. 

This type of conditioning goes beyond just running sprints because it requires the players to be explosive in getting the bags into a position that they can carry them and it requires them to do a weighted sprint.  I highly suggest this for any athlete looking to improve their game.