B to C# on the staff would be better. If you have a really proficient flutist, they should be able to "approximate" a gliss between those notes, but it will not be really smooth because those are not open holes either. It really depends upon the tempo. A slower tempo will allow the flutist to play B-C-C# and bend the pitch on each to get a bit of a gliss effect. At fast tempos, it's probably going to sound more like a chromatic progression between those notes. It also might be possible for them to start with the C fingering, but bend the pitch down to the B (or as close as they can get) lip it back up to C and then repeat that while fingering C# so that the gliss/pitch bend ends on C#.
If the flute is not playing immediately before or after the gliss, a really good B-to-C# gliss can be obtained by removing the headjoint from the flute. The flutist must stick a finger into the open end to get the B, and then withdraw the finger until the C# is reached. This produces a slide whistle-like effect. Of course, this requires a flutist with a really good ear (or tuner) to get the right starting and ending pitches.
It might require some experimentation by the flutist to see what works best.
I hope that helps!
"Never give a flute player a screwdriver."