First, pry the end plug out of the handlebar.
Slide a zip tie under the grip to create a gap, then flood the gap with rubbing alcohol or spray window cleaner. The zip tie only needs to go in about 1.5" to provide the gap required. Pinching the grip to open a starting place is helpful. The alcohol/cleaner lubricates the grip which can be twisted and slid off the end of the handlebar. Remove both grips.