Simple carbs, electrolytes, water. Same composition as you’ll have on the bike. Drink it ~15-20min prior to riding. Not 30min prior. Make it the night before, for ease of access in morning. Store in fridge or add ice in morning if temperature regulation may be challenged due to indoor riding.
Worry about getting a balanced meal after training with protein, fiber, fat, and of course more carbs and fluid.
The only goals in short-turnaround pre-workout consumption should be:
- Elevate blood sugar
- Top off hydration
- Avoid gastrointestinal distress.
No special fueling the night before is necessary if you’re consuming carbs around the clock, as normal. Any consumption the night before just serves to top up glycogen stores, and there is no special need to do so at night, when training first thing the next morning. Feeding with carbs late at night won’t result in elevated blood sugar (goal number 1) pre-training for your first-thing session. That’s not to say “don’t do it,” but just to say that any focus on this nighttime feeding is unnecessary assuming normal dietary habits with sufficient carb consumption.