I bit off more than I could chew yesterday.............
That says it all. I think you need to work up to something like that with better training etc. Mild nauseous is not a good sign. Could be from heat, overexertion, or both but your body just told you too much right now. Not a food or hydration issue. You can't eat or drink your way to fitness. IMHO you had plenty of both for this ride. Maybe better, more measured water intake. Do you sip water every 15 minutes or so or do you wait and chug?