Some Sugars such as Sucrose are inexpensive to use but are hard to work with for one reason or another.  Others, such as Sorbitol are low melting and easy to work with but are more expensive.  A number or different reasons exist that would benefit the mixing of different fuels for improved properties/economics.  This page lists some test stand data on some of these mixtures.

MIXED SUGAR FUELS

238 KNSU/SO mix  (25 SU/10 SO) + B-1
Propellant mass = 119.8 g = 0.264 lb
Throat area = 0.0372 in2
Thrust duration = 1.56 sec
Max Thrust = 26.8 lbs
Max chamber Pressure = 515 psi
Ave Thrust = 18.1 lbs = 80.5 N
Total Impulse = 125.6 N sec = 28.2 lb sec
ISP = 107
Motor class = G81

Fuel very flexible.  Still exhibits "slow
slump" after one week.  Pourable.

238 KNSU/SO (27.5 SU/7.5 SO) + B-1
Thrust duration = 1.60 sec
Nozzle Throat = 0.3565 in2
Propellant mass = 122.8g = 0.270 lb
Max. Thrust = 32.0 lbs
Max. chamber pressure = 640 psi
Ave. thrust = 21.4 lb = 95 N
Total impulse = 152 N sec = 34.2 lb sec
Isp = 127
Motor class = G95

Fuel less flexible.  Easier to work with.  Pourable.

238 KNSU_SO (7.5% SO) B-1 (repeat)
Thrust duration = 1.65 sec
Propellant mass = 123.1g = 0.271 lb
Nozzle throat = 0.0333 in2
Max. thrust = 29.6 lbs
Max. Chamber pressure = 540 psi
Ave. Thrust = 21.3 lbs = 95N
Total impulse = 156 N sec = 35.1 lb sec
ISP = 130
Motor Class = G95