As with all Exodus trips, carefully read the, "Is this trip for you", section on the trip notes. If there is nothing major that puts you off, then book it, you will not be disappointed.
I rode with open toed sandles, (Merrells), they were great, but dont forget the sunscreen on your toes. Padded undershorts are a must, without pants or knickers, (they will be the most likely cause of irritation), over-shorts, cycling shirt with rear pockets to hold your camera, tissues, and anti-bacterial gel. Girls, sports bra is recommended. A full length zip for the shirt is good to allow for max ventilation. Four sets of shirts and undershorts, two pairs of over shorts, (knee length as this will get you in to temples etc), is more than enough. Take a one litre water bottle for the rides, and aim to drink most if not all between stops when you can re-fill. Personally I wouldn't bother with a back pack or hydration pack as these will just weigh you down and make you sweaty. Don't bother to bring your own snacks, (unless you have special dietry needs of course), as the tip/snack kitty will cover everything you need.