The main alternative is travelling around Cape Agulhas at the south of the African continent. This is the route for ships which are too large, and was the route before the canal was constructed and when the canal was closed.
In the early twentyfirst century this route is often taken due to increasing piracy in Somalia and the high canal dues.

Before the canal's opening in 1869 goods were sometimes offloaded from ships and carried overland between the Mediterranean and the Red Sea.

Napoleon discovers an ancient canal
Operation
Alternatives
Old Cairo to the Red Sea