Ice cream sandwich has probably half the sugar of a can of coke, fewer calories, no caffeine, and won't f*** with your teeth as much.
Either way, a can of coke a day isn't going to hurt you if your diet is otherwise in check.
Seeing the s*** people shove into their faces at work for breakfast/lunch is mindblowing. Muffins/egg sandwiches/bagels and cream cheese for breakfast and pasta/hamburger/fries for lunch. I'll never cut out carbs completely, especially with dinner, but for a few years now I've been fine with fruit for breakfast and either soup or a light sandwich with vegetables for lunch.
I drink about 5 liters of water a day. I never get sick, never get headaches, and generally feel healthy all the time. I don't know how much drinking water has to do with that, but never being dehydrated certainly helps.