Depends on the excursion. Am I going to Disney World or hiking in the mountains? Assuming I am out in nature I would bring:
1. Water.
2. Something to eat. If I am going to be gone a full day, more than 8 hours, it will be more than just a granola bar probably. Piece of fruit, maybe a sandwich, nuts or chips. I’d put the food in an insulated bag to help keep it at temperature for at least a couple hours.
3. Compass if It I am out hiking on a confusing path.
4. My phone if it will work where I am going.
5. Cash, a credit card, and ID.
6. Suntan lotion and sun protection for my lips.
7. Bug repellent.
8. Wet napkins like the ones they give you in restaurants that serve ribs.
9. A couple bandaids and antiseptic of some sort.