Before any ride you should be fully fueled - eaten appropriate food, enough of it, and drunk enough to be fully hydrated. See the answer by mattnz regarding electrolytes.
Just before you start have a good drink, then drink a little and often on the ride, before you feel dry or thirsty. After the ride make sure you drink plenty, and eat a balanced meal.
But perhaps you aren't normally properly hydrated (like most people), and this caused a problem last year. If that's the case, then it's not just the day before - it should be every day! Kidney damage due to lack of hydration is common.
Whether a given ride is tough or not depends on two things
The MapMyRide page you link to is a bit deceptive, suggesting that the climbs are around 2%. On Strava I see that there are multiple short climbs of 6-7-8%, some of 10-12%, and a few short pitches up to 16%. I see that the longest climb is in the last 5km. Most people would agree that those steeper gradients can be tough, so I would focus on some climbing practice, rather than worry about water. Manage the water, build your strength.
In summer the climate in Perry is very mild (82°F, 28°C), so unless it's unusually hot or windy, it will not be an issue. Just carry two full bottles of water from the start. You didn't ask about food, but it looks like a one-banana ride to me. Eat half after an hour, the other half an hour later.