Data packs for all cars/series are scheduled for release by Sunday 23:59 GMT each week for the following weeks track. So if the VRS GT Sprint Series visits Fuji Speedway for Week 2 of the season, then the data pack for this combination would be released by Sunday of Week 1 giving you plenty of time to practice for the upcoming week.
Occasionally coaches may release packs a little earlier or later based on their availability, keep an eye on the specific Discord car channel for updates each week!