Do you have a wet/dry vac? If you're afraid of getting the glass stuck inside of the vacuum, use some panty hose and put them on the end.
Most disposals are fairly easy to take off. You might be able to pop it off and get a better reach.
Also, most have an allen key on the bottom that let you turn the entire motor assembly by hand. You might be able to force the movement of the disposal.
If you flip the switch & the garbage disposal just hums & does not turn , it is jammed
FIRST: TURN OFF THE POWER
Turn off the power for the garbage disposal at the main circuit breaker.
Test to make sure the power is off by turning the switch to the ON position. If it doesn't hum now the power is off
Turn the switch back to the OFF position.
If it still hums you have not flipped the proper breaker switch , go back & try to figure out witch with breaker is the right one for the disposal.
Some garbage disposals have a plug under the sink , in that case just un-plug it.