These are given in cards for the use of buying things within DMWL, these include:
And other such things that can be bought, there have also been times where guards have tried to take the cards to add to their own pockets. Be warned though, you have the right to try to bribe a guard, but it also depends on that guards personality--if they are nothing like the way you think they would be--don't try it.
It is also certain that if the head of the guard is the same way--chances are you'll end up getting into more trouble than getting out of it.