I’ve also dropped an email to SBS Transit to enquire if eating or drinking in the bus is still prohibited by the law. However, I have yet to receive a reply. When it comes to such issue, my take is that a lot have to come from self-moderation of the riders. I believe it is ok for a passenger to take occasional sip of water on the bus as some journeys could be long and there may be traffic jams along the journey. However, it is not right for someone to munch on a hamburger or French fries during the journey. Such a person is blatantly trying to challenge the law and I have encountered such passengers.
Whether or not eating or drinking on the bus is still prohibited by the law, it is the social responsibility of every passenger to keep the public transport clean.