I have classes the Saturday before I flush! What should I do?

I have an nine-hour class the sixth day of preparation for the flush. I'm following Andreas Moritz 's protocol, and by time I get home from class (around 8 or 9) it will be too late for the first Epsom Salt drink (which is around 6pm) I can't push this back another week because I've already bought apple cidar, which will spoil within a week. Can I pack the Epsom drink in a glass jar in the morning and gulp it down in class as an alternative?? Does Epsom Salt make you gag?