This may work in Singapore, but I would say it has limited appeal as-is, elsewhere in SEA.

There is some friction to finding and stopping for a snack in the west, whereas there are little street-side stalls selling drinks and snacks every 50 yards in most SEA cities, and the transport is often tuk-tuks and rickshaws rather than taxis.

Additionally, I doubt people will be willing to pay for premium western brands (which they're possibly unfamiliar with), with a further captive-audience premium, unless there's a "conspicuous consumption" aspect to it - rather difficult in a vehicle, as opposed to a glass-fronted coffee house for example.

Good luck nonetheless - they may have some success with the right products, though I can't think immediately what those would be.