Legally a turnaround is NOT considered TWOV. See Timatic:
R32) TWOV
....
Transit Without Visa (TWOV): Passing through an international
transit area of the airport in order to board a connecting (or
to proceed by the same) flight, without entering the country
(i.e. clearing immigration).
Unless stated otherwise, passengers wishing to TWOV must:
- be en-route to a third country (e.g. itinerary TYO-LON-TYO
is not considered TWOV);
- prove that they will continue their journey within the
prescribed period (e.g. hold onward tickets or proof of
sufficient funds to buy an onward ticket);
- have documents required for entry into the country of
destination and for transit through countries en-route;
- remain in the transit area (airside).TWOV is not intended
for those holding ISA (If Seat Available) tickets, e.g.
airline staff or other passengers travelling on industry
discount.
My emphasis
If I were you I would buy a refundable ticket to a third country and cancel upon arrival in Sudan.