I try to avoid preworkouts supplements as much as possible. If you look at the ingredient list, they've got so much chemicals and compounds in there, it can't be healthy for your body. Any one of those ingredients could be giving you the headaches.
I usually skip eating when I'm out in the woods and then make up for it with a large meal when I get back. As far as I'm concerned, the amount of calories you need in a day can be split up into multiple meals or through one big meal, makes no difference.