Personally I've never needed that. Experiment and try, go wihtout the carbs but maybe some coffee or green tea 30 minutes before, and if you burn out too quickly, which you shouldn't after only 20 minutes, try adding some carbs. White bread and jam would be far down on my list though, how about ripe bananas or rice, or maybe even better some whey and mct?
Ideal would be to time your meals around your workouts. It's not an exact science, but somewhere around 1-2 hours prior to the workout, depending on meal size (and timing of the meal prior to that), would be good IMO. It's trial and error as you have to determine what macro split (and meal timing) makes you feel best and gives you the best energy. Some do better with more carbs, some do better with less. I find a lower carb meal works best for me, but I generally eat pretty low-moderate carb. If given the choice of steak or pasta before or after a workout, I would choose steak 99% of the time. The goal of the meal is to normalize blood sugar level around the time of the workout. Then for sustained energy, fill the "gaps" with something like SWF or finibars if you are going to be training for longer than about 30 minutes. This is if fat loss is not your goal, but of course you said "conditioning workout," but I just wanted to be clear. If your conditioning is less than 30 mins you don't really need anything additional IMO, besides maybe some BCAAs and possibly some electrolytes.
Cool thanks guys. Yeah I believe yous are right as I actually do feel quite good without carbing up on a meal before my workout. But I also feel good taking in carbs. Sometimes when I dont eat carbs I 'think' that my workout maybe suffering, but I think it is all just mental as thats just what you read nearly everywhere.