You are welcome to bring snacks and food onto a charter bus in most cases. Discuss your plans with the company while booking and ask if they can stock the bus with refreshments for you. Each bus rental service has different contract terms about beverages and food onboard.
Always ask if there are any specific items you can't bring onto the bus because penalty fees can apply if you breach the contract. Companies often prohibit bringing flammable items, illegal substances, and weapons onboard.
Smoking typically isn’t permissible on the bus.
If you plan on bringing alcohol, ask if they require a special deposit to cover cleaning and incidentals beforehand.