What notes dont have sharps on a 4 string bass guitar?

Regardless of the instrument, the scale is always the same.

Remember this: In The Simpsons, Homers Barbersharp Quartet was called the BE sharps. This is an Excellent way to remember because B and E are the only notes without sharps

By the same token, this means that the note above B i.e "C" does not have a flat and the note above E i.e "F" does not have a flat