The Jupiter vrat is kept on Thursday — traditionally one meal after sunset, without salt. It is the household remedy for a weak Jupiter, and unlike a gemstone it cannot be kept against your chart.
The weekday fast is the household remedy — kept on the graha’s own day, usually one meal after sunset and no salt. It is as much a discipline as a ritual: the point is the weekly act of restraint, held long enough to mean something.
The Thursday fast is vegetarian, eaten once after sunset, and traditionally uses yellow foods — chana dal, turmeric, banana.
An afflicted Jupiter reads as poor judgement, lost opportunities, difficulty with teachers or children, and a loss of faith in one’s own direction. Thursday observance and service to teachers are the classical answer.
Thursday. Fasting, charity and mantra japa for Jupiter all belong to that day.
The mantra, the weekday fast and the charity are safe for anyone — they address Jupiter without amplifying it. Yellow Sapphire is not: a planetary gem strengthens whatever the graha is already doing, so it needs a chart reading first.