Nutrition on the road - What, How and Why?

Also is there like an optimum time for eating before?

No

I'm kinda hoping to have a lazy day with a sleep in the afternoon but make sure to drink plenty of water so when I start I'm well hydrated. Don't want to eat too late or too much or anything and give myself a crippling stitch or whatever the nice side effects could be.

On a ride like the DD, unless you're absolutely set on hammering to clock a really good time, you won't get a crippling stitch.

I've done 5 DDs and a handful of audax rides and have tried various eating strategies for them. In my experience you could have a decent size meal right before starting and not feel any ill effects save feeling a little uncomfortable trying hold onto some of the faster wheels. You might also suffer some burping and heartburn depending on what you eat.

Drinking plenty of water through the day isn't a great hydration strategy. Sure your water levels will be up but without some food mixed in to soak it up you'll just as likely end up interrupting that afternoon snooze with lots of peeing and washing out salts that you'll need later on.

Best thing I can advise is that in the three or four days leading up to the ride is to eat normally, drink a reasonable amount of fluids and avoid things that will dehydrate you such as getting pissed or doing lots of exercise.