Is my driver drinking on the job? (Jakarta)

This evening I got out of the car and looked in the boot of my car to see if there was 12v outlet so that I can install a fridge for beer : Protected content , upin doing so my driver seemed very sheepish and I found an nearly empty bottle of Bombay Gin, mixed in with bottles of water and next to his cleaning gear. Should I give him the benefit of the doubt and assume it was for cleaning windows or would you assume he's drinking on the job? If so, chat to him about it or....