Slice the cooked chicken breast, if needed, and cut the pita into wedges. Portion the tzatziki into a small lidded container if you're using homemade.
Assemble
Arrange the chicken, cucumbers, tomatoes, and pita inside a compartment lunch container. Add the container of tzatziki, or pack a single-serve cup alongside the lunch.
Pack for Lunch
Refrigerate until you're ready to place the lunch container inside an insulated lunch bag with an ice pack, if needed.