Nearly half of the rest areas are not operational on M5 as yet, but there are at least 2 rest areas on M5 between Sukkur and Multan which serve Petrol. One is at Och Sharif rest area the other I don't remember now as I traveled last month on Oct 11 (up) and 18th (down). There are 2 types of rest areas presently operational, one are very small ones with a shop for snacking, whereas the bigger rest areas have got very good, clean washrooms and a couple of restaurants too.
Refueling just before entering M5 is the best option.
Just an additional info: Royal Taj, Moro is a very good option for breakfast and they also have good/clean washrooms and Indus Highway (Hyederabad-Jamshoro-Aamri-Qazi Ahmed) will save you about 1 hours' drive time. Although it is a single carriage most of the way, but a very good newly carpeted road 95% of the journey.
I'm trying to attach a video of Och Sharif rest area, you can see a fuel station too. I'll try to attach one more in due course of a close up of the same.
Closer look
