If it's the first paycheck you've earned in five years and you can't afford to eat out once a week without the donation, and you have a lot of debt, it's likely you have little or no savings. If so, I would suggest putting the $100 in the bank in preference to either eating out or CFAR. You never know when a $100 expense might come up.

Furthermore, you should be paying off the debt anyway. Put it this way: Imagine that instead of you coming into possession of $100, someone were to shave $100 off your debt directly. Under those circumstances, would you go into $100 more debt (cancelling the effect of reducing it) to be able to give some money to CFAR? (Ignoring the fact that you probably can't borrow in increments of $100.) If you wouldn't increase your debt by 100 to pay CFAR in the first scenario, you shouldn't pay CFAR in preference to reducing your debt by $100 in this scenario.