Sara - Doing your workout after work when you're on days sounds like a better idea, since you'll have your glycogen stores at a normal level. It also opens up the possibility that you'll be able to ride outside as the days get longer rather than on the trainer.
Re: breakfast before the workout, is the reason you don't eat due to not liking to eat first thing, or time? If the latter, a possibility is slamming a gel followed by some water, and/or using sports drink while on the bike. That might get enough sugar into your system to power you through the workout.