Eating before early morning hard classes

I teach twice a week at 6 am, and it's a 30+ minute drive to get there, so I get up at 4:50 am on those mornings. I don't do well on early breakfasts - it's just not comfortable putting food in my system that early. I would rather not eat (and sometimes I still don't) but I do understand the importance of eating something before exercising after a long fast, so I usually nibble on a piece of toast or bread, and maybe a banana or a little yogurt. In a rush I'll eat half an energy bar, but most have too much sugar for me (even the low sugar ones).

I've often stressed to my class the importance of eating something beforehand, but I know some of them live very close to the club (it's a neighborhood community club) and they were probably in bed only 15 minutes before!

If I am planning a hard class, at threshold or above, I think it's even more important to eat something. Last week I did a threshold field test, with a 20-minute hard sustained effort (plus an initial 5-min hard effort in the warm-up). In their preparation materials prior to the field test was the suggestion that they should be well hydrated and fueled prior to class, even if they had to set an alarm to get up earlier just to nibble on an energy bar. (Note: this is a 12-week periodized cycling clinic, so I have the same students every class and I send them a coaching email weekly with training tips and that week's goals).

One of my students emailed me afterward that she felt nauseous and light-headed after the field test. There could be several reasons for this, including factors such as illness or fatigue. It could also be because we've only done minimal higher intensity work, and certainly it was the first time we spent that much time at that intensity since the first field test 7 weeks ago. I don't believe in throwing a threshold field test at them after 6 weeks of base building in zones 2 and 3, so last week we did some sub threshold intervals, up to about 2-3 beats below LT.

She is a fit woman who does a lot of skiing and snowshoeing (which are higher intensity sports here in the mountains), so more likely it was either not eating, or what she ate. She said she ate toast with peanut butter about a half an hour before the class. Peanut butter has protein, which is a good thing, but for me, anytime I've tried it that early in the morning, I didn't feel well during my ride either. She said she would try something else for our next field test.

I'm curious. For those of you who teach or train early in the morning, what do you eat, and how early before your workout do you have to eat? Have there been things you've tried that have proven not to work for you? Does anyone have a problem with peanut butter early morning, but not at other times? I'm sure there are those of you who do not eat that early before class. It's probably OK for a more aerobic-intensity ride (as long as you eat soon afterward), but do you feel a difference during higher intensity rides if you've not eaten anything prior?

Thanks for your comments. I might try to get an exercise nutritionist to look at these questions and give some advice that we can all benefit from!