Aunty at check out counter is a gem! Always ready to help and so polite. There's a wife range of alcohol, fresh fruits, confectionary, yoghurt ... Good place to grab and go in the area if you're not looking to dine at a restaurant or a cafe.
A nice, clean, well-stocked convenience store opposite the Marina Bay Sands hotel. Lots of chilled food, snacks and drinks. It's not so hard to find - just near the entrance to the shopping centre by the taxi rank. Ground floor level.
Great supermarket, product price even lower than airport (duty free). Bottle of water is much more cheaper.