If one can’t do anything for anyone, one can surely do just one thing. One can make dua for him/her.
There is a very short dua which can be recited in just 5 seconds but is very heavy on scales.
The dua is, ‘Allahummaghfir lil muslimina wal muslimat, wal mu’minina wal mu’minat’ (Ya Allah please forgive all Muslim men and women, believing men and women). One who recites this will get the reward equal to the number of Muslim men and women living on the earth.