There is a person who gave me a free lunch today. I don’t really need it. Is it better that I should give it to a bachur (chesed) or to give it to the goyishe painters who are painting my apartment (kiddush Hashem)?
When giving it, (to either one), should I inform that I did not pay for it, or say from whom it is coming, to avoid genevas daas?
You should give it to the bachur, the reason being that we are obligated to give priority when doing chesed to our fellow Jew. Regarding informing him, I don’t think that he is going to think that all of a sudden you decided to pay for his meal, and he will understand that you got it somehow, but if you want to tell him you can.