Yes, we can drink in uniform. You can even consume an alcoholic beverage during the duty day. We call it "Beer Friday" and often get a beer at lunch on Friday or will have a drink or two at a Commander's Call at a bar after work on Friday.

Military professional would tell you not to get drunk but having one or two is more than acceptable (unless one has a duty that has alcoholic beverage restrictions such as a pilot or aircrew member about to go on a flight - our policy is 12 hours "bottle to throttle").