If the beans are flavoured, then the grinder will be afterwards as well.
Best not to put the beans through any grinder that you want to use for regular beans at a later point.
If you really wish to try them, perhaps look at a cheapie blade spinner thing (spice grinder) and doing the flavoured coffee in a plunger.
Or, my personal choice, put them in the bin.
If the person that gave them to you ever asks, say they werent to your liking.
For people who really wish to try the flavoured coffee thing, I think syrups are a better way to go.