For example in your case, prior to the start of the season you establish the rule that any unexcused absence from a practice may cost you to sit down for of the next game, or a specific game. Unexcused absence from a game will cost you your position on the team. The rules are clear, the negative reinforcer is not being able to play. If the player's shrugg their heads and say they don't care if they sit, this would be a good indicator to me they probably don't belong on your team. This might cost you a game, but being unresponsive to lateness or unexcused absences will cost you more than a game over the course of a season, it will more likely cost you respect of the players and eventually your job.
Punishment differs in that the consequence is unexpected.
You might say for example to your team who arrive late, get on the line and run. Punishment seldom produces the desired affect and should be used judiciously like the jockey whipping a horse. If you whip the horse in unexpected ways from the start of the race on, your horse will not respond when you really need to get their attention. In summary, be sure you have thoroughly thought out all the possible scenario's for late or unexcused absences. Do not surprise your players by punishing them for guidelines you haven't set.