Soda cards are subjective. If you routinely drink more than 4 cans of soda a day perhaps they are worth it. I personally do not endorse them except for kids since it facilitates their getting something to drink without an adult. You can bring a reasonable amount of bottled water aboard on embarkation day. I define reasonable as a twelve pack per person.
Doing any of the Mayan tours means you need to have comfortable walking shoes. I mean running shoes, or something like that. Too many people show up with flip-flops and other flimsy sandals or shoes and they regret it. I don't understand why some people wear inappropriate footwear to places that clearly call for more substantial shoes. I guess they don't have what we in the south call 'walking around sense'.