Is there any source for making brochas on food and alcohol (lechaim’s), for a le-ilui nishmas for the yortzeit of family members? (as I have seen people bring food to the shul along with alcohol for yahrzeit and tell people to make a brocha in their name)?
There is no formal source for this, to my knowledge. However, the general idea is that every mitzvah can be an iluy neshamah for the niftar, and making the berachos on food with the intention of the niftar is therefore worthwhile.
The custom is mentioned by the Penei Baruch (39:34), who mentions that this implies “chasing after mitzvos.”
Some state that the custom of bringing food comes from the custom of making a siyum, which permits a person to eat on the day of his yahrzeit — a day that he should be fasting on. Over time, the idea of the siyum was forgotten, and only the food remains. . . The Penei Baruch also writes that bringing the food is seen as a substitute for fasting.