Once my workplace had a party/fair allegedly to raise money for some charity.

I was slightly miffed to the low util to fuzzies ratio, and to the company's taking the credit for the employee's fundraising, with no corporate matching.

So, when I was asked for money at the event (one-on-one, not in front of everyone), I wrote a check to my favorite charity, for about the same total as the entire fundraiser, right in front of the person asking for the money; I explained myself politely and the requester (I think) took it as an impressive act of charity rather than as asociality. The check was in addition to my usual monthly donation.