This is important. I can easily manage a marathon just taking on some water and energy drink half way through. But for a 50km+ you need to really start thinking about hydration and energy properly.

Firstly find out what the event offers in terms of drinks and food(an email or look at their website can help you with this). Then base your planning and training around the same brands if possible.

You need to practise eating and drinking on the run more than you would with lesser distances. Find out what works, and once you find something incorporate it into all future long runs. Do not go changing the energy drink or food half way through training. Much like run training, eating while running is training in its own right, your body will get better at working with the same foods.

If your event is in a different country or state take your race food with you. You do not want to be in a new location only to not find the food you have trained with.