The secondary Egypt exhibit at the Cinquantenaire Museum is accessible on both a Sarcophagi and a general-admission ticket and is located on the top floor of the museum.
While their Egypt collection is amazing in its own right, displaying many pieces you won’t see anywhere else, it is treated a bit like the unfavored stepchild. Everything else is beautifully presented, yet these are all simple displays and often the lighting is bad, which is a shame. Some pieces have also been moved (possibly to Sarcophagi), leaving ugly empty gaps.
If you have bought a Sarcophagi ticket, I would advise seeing the Egypt collection and Djehutihotep first, because if you see them the other way around you will be totally underwhelmed.
Djehutihotep is interesting, giving you a glance at the archaeological process from back in the day. The addition of tools from the era is a nice touch. It is just too bad that the exhibit is tucked away in an almost forgotten corner of the museum.