I agree with a lot of some of the suggestions others have shared, like warning them ahead of time. Here is something I don't think others have presented:
When my son or daughter is very upset about something, I explore that feeling and experience with them as much as possible. I sit with them and acknowledge they are upset. (If they let me get close to them) I will comfort them physically. I use observations like, "I can see you are upset", and comments like, "You really want mommy", etc. I ask them questions such as, "Are you upset?", or "Do you want Mommy to hold you?", or "You want to eat mommy's breakfast?" I continue with this mode of welcoming and accepting of their experience continually as they are crying, etc waiting for my child to shift and reciprocate back to me in some affirmative way "Are you upset" : "Yes!" (while still crying).
This accomplishes 2 things: 1) affirm how they are feeling and 2) introduce tools for using words to express how they feel (instead of just crying). You can even have fun with your questions like, "You want mommy to hold you forever and ever and ever?", or "You want to eat all of daddy's breakfast?" The best outcome is that they are able to use words to describe how they feel and for you to be welcoming of that. There is no 'solution' to your child's problem without FIRST just empathizing and allowing them to be heard. After that, you may find that that is all they needed.
I think society's general approach is to distract from these feelings, but this can have the underlying current of rejecting how your child feels and not giving them the chance to express that. Trying to come up with distractions such as breakfast, a book, or some other routine may seem fine, but when we are inclined to avoid uncomfortable feelings, we need to go out of our way to accept and welcome them as a normal part of being human.
An important point that goes along with my suggestions is that your child (younger than 5) is not a rational person like you are. They don't have the intellectual mind that can rationalize and reason- they are very much in the present moment feeling whatever they are feeling. Therefore, trying to reason with them will be particularly frustrating.
I want to emphasize, the goal is to be totally accepting of those 'unreasonable' feelings. Obviously your child's father must go to work. You don't need to explain that (I think it is healthy to say it, but I wouldn't spend much time trying to justify it). Instead explore their feelings as much as possible. And when they calm down, that is when you need to go even further with exploring how they are feeling, because now they have the capacity to deeply acknowledge how they are/were feeling without being totally overwhelmed by it. I think it is tempting to be thankful they have finally let go of it, finally stopped crying and just not bring it up again. But this is the perfect time to re-acknowledge everything they were upset about and continue to introduce the words they can use to verbalize their feelings.
Don't try to prevent the crying. Embrace it and explore their feelings with them. Introduce words/phrases/sentences they can use to verbalize how they are feeling. Continue this even after they have calmed down (as they now have more presence of mind to learn how to verbalize).