Like accommodations the choice for places to have food or drinks is a little bit limited, but you can et some delicious sea food or fish freshly caught. It would be a shame visiting the island and not taking advantage of that.
In Bai Lang village there are several little cafes and food places at the road along the waterfront. They look nice and busy with locals. Staying there for a drink might be a good opportunity to talk to some of them.
For day trippers they usually head to the food places along Bai Chong Beach – of which there are 4 or 5. It seems each agency organising trips to Cham islands use a specific one. I had lunch, dinner and breakfast at the last stall on the beach on the left (looking towards the water). The dishes, ranging from fish, seafood to pork and beef, tasted very good. For breakfast you get eggs and baguette – simple but lovely.
For a coffee break near the beach I would highly recommend the Ecological Garden Hill, which is a few minutes away from the beach – as it is located overlooking the beaches from the hill behind it. Just follow the stairs to the road, and you will see more stairs to your left that will lead you to it. The owner is a very friendly man, who does not speak English. The drinks are nice and cheap, and you have a spectacular view from the seats. If you ask, he will show you around his land as well. Worth while the little effort to take on these stairs.
So while the places to visit is limited, the food on the island can be very good – for a low price.