When you put a plant in direct sun, it starts to transpire very fast because all that light makes it use up water to make sugar (the primary reaction of photosynthesis requires the water molecule to donate a hydrogen to the new carbohydrate molecule).
You can slow it down by decreasing the light intensity.
Also sniff around the drain hole of the pot and if it smells funny, you have a problem. Root rot is the other cause for a plant looking close to death all of a sudden like that, and it's the reason to have LOTS of drainage and only water when the soil is dry.