I, too, have to be careful of sugar. I carry:
Nuts (cashews, almonds, sunflower seeds, etc.), pepperoni stick, cheese stick, peanutbutter and celery (or pretzel sticks), beef jerky, snap pea crisps.
Hope that helps! For a treat, the candy store by Winnie the Pooh has some great sugar free options, and in DCA Clarabelles has a no sugar added butter pecan Ice cream.
No one in our group has any special dietary needs.. but definitely agree on the nuts! We ALWAYS bring nuts to snack on.. favorites being almonds, walnuts, cashews, and sunflower seeds! So good. Apples are also handy and don't need any prep to eat! Also love to bring in some cherries as they help aid with muscle soreness which comes in handy when you spend the majority of the time on your feet and walking EVERYWHERE!
We used to bring nuts but now we don't even bring that because snacking just isn't good for our diet even if the food is healthy. We've learned that it wont kill us to be a bit hungry for a little while until our next meal.