Besides accommodation, you’re free to offer travelers whatever other benefits you’re able and willing to give them. The more rewards you offer, the more interested travelers will be in your position. You can offer them daily meals, such as breakfast, lunch, and dinner, and/or the possibility to use the kitchen to prepare their own meals.
Apart from food, you can also offer them free tours around the city, free classes (languages, yoga, permaculture, etc), free laundry, discounts on local restaurants or bars, and much more! You can take a look at all rewards you can offer travelers on your position’s page (Profile→ Volunteer Positions → Edit → Your Offer).
Remember, it’s always a good idea to offer meals, classes, discounts, experiences, and other rewards to travelers! Some, for example, might prefer positions that have breakfast included over the ones that don’t offer any meals.