Cakes are associated with special occasions and celebrations so if you saw cake in your dream it is generally a positive sign about your life in general and those who were in the dream with you. Perhaps you were sharing cake with your work colleagues because you work effectively together and get on with those you spend 8 hours a day with. Maybe you consider them to be special people in your life despite where you met.
It can also be indicative of overindulgence, however if the dream felt positive for you- it can be a sign you have a lot of love in your life, whether you're aware of it or not. This doesn't necessarily need to be be from your workmates, but friends, family or a partner.
If you ate and enjoyed the cake then you may be feeling a great sense of satisfaction and fulfilment in your life at present. The phrase 'piece of cake' comes to mind- it is possible that you are finding life quite easy now because you're in such a good place.
Alternatively, you may feel that in your professional life you deserve a reward or recognition for your hard work. This might take another form, like more money, a promotion or a simple 'thanks' but masqueraded itself as cake in your sleep state.
Another line of thought is that you enjoy short-term indulgences and sacrifice your long-term goals as a result. Do you spend money too quickly rather than squirreling it away? Do you tend to walk away easily from challenges by doing something you enjoy? If you felt guilty about eating the cake it's possible that you feel you're doing something in your waking life that doesn't sit right with you. Or more simply- if you are dieting right now and things like cake are forbidden- maybe you felt guilty for eating it in your dream because you know it's going to sabotage your weight loss goals.