I've toured quite a bit in tropical climates in Asia and Latin America, and have had no problems as long as I drink plenty of water and other fluids, and eat regularly and reasonably. I generally try to start riding early in the morning and avoid riding in the worst heat of the day. In addition to drinking plenty of water, I know that in some countries (e.g. Laos) I was spending more on drinks than food. Both were extremely cheap.

If I'm riding somewhere where food and drink is not readily available, I carry plenty of food and more water than normal. It's not rocket science.