Sudanese travel visas can be expensive and difficult to obtain on your own. It is best to try and get your visa in your home country, though it can sometimes be obtained in Egypt, or we can obtain them from the government here.
If you are in Egypt and a little lucky you can obtain a visa within a day of application. For most nationalities it costs US $100 and requires a letter of introduction from your embassy.
In Ethiopia, getting a visa from the Sudanese Embassy in Addis Ababa is unpredictable. If you are lucky it costs about US$60. The embassy will send your name to Khartoum for approval, which as they say could take two weeks or two months. Once approved, the visa itself only takes a couple of days. Expect to wait at least two weeks for approval.
In Kenya, the Sudanese Embassy in Nairobi sends your name to Khartoum for approval. The time it takes is similarly ambiguous, although the embassy is far more professional and efficiently-run than Addis Ababa’s.