Next day:
When can I drink water? - Right after your last Epsom Salt drink.
Can I drink Organic apple juice? - you can drink and start eating as soon as you feel like it - after your last Epsom Salt drink.
Also...I know a few people who drink water up until just 1 or 2 hours before their first Epsom Salt drink. I know I do! (and some others do too and still have successful flushes..and are well hydrated) You can experiment and see if it works for you...