If I were going to take your yogurt from the fridge at work (which I’m not), I would find a way to do it, even if your initials are written in black sharpie at least 4 different places on the container. I know I didn’t put the yogurt in there in the first place. You have the only five containers in the fridge. If you are worried about not knowing which ones are yours, put a dot or something on the lid. Maybe even your initials would be ok – once. Or you could just finish the job and color the whole thing black. That would probably be the best deterrent; anyone who messes with your stuff would get black marker on their hands. I would be like reverse fingerprinting the scene of the crime. Unless they used the safety gloves from the cabinet. Those smart criminals. Then you’d just be out one untraceable yogurt.
Also: Other people use the sink. Wash your stuff and take it with you.