Serve carbonated beverages from a beverage gun or dispenser (i.e. postmix) rather than by the bottle or can. If you have to use bottles, recycle them along with wine and liquor bottles. If you can or already do use a postmix system, and use reusable syrup canisters rather than the bag-in-the-box alternative. This way, the boxes don't get thrown into the garbage.
Use straw-style stir sticks for bar beverages instead of the solid style. They cost less per unit and use less plastic. Additionally, use only one straw per drink.
Serve straws from health department approved dispensers rather than offering them pre-wrapped. At the same time, consider purchasing straws with a smaller hole size than the ones you are currently using.
Purchase products that are packaged in ways that can reduce the amount of material being disposed.