Ask the riders what they bring for hydration/nutrition. Using larger bottles (30+oz) and adding a third in jersey will just about get you there. Load them up with calories/electrolytes and bring gels and other quick calories.

If you are the weakest rider, do very short pulls at the front. You will be helping the group by just working in the paceline, moving up and helping the draft. Once you get to the front, peel off relatively quickly and get back in line. This will be much preferred over longer pulls that slow you down at the end due to burning out.