I think you misinterpreted the initial post. The poster was asking what he should eat before and after his CARDIO workout. No way should you eat dextrose and whey just before cardio. LOL.
When cutting, many people find it better to do cardio first thing in the morning on an empty tank at 65 - 75 MHR for 20 - 30 mins to tap into fat stores. At this HR, the calories you burn will mainly be from fat. After cardio, have your regular killer breakfast of carbs and protein. If you lose muscle easily you may want to have a whey shake (whey + water) before and some BCAA's immediately after (i.e. before you hit the shower).
Alternatively, you could do cardio after your WO as your glycogen stores will also be depleted at this time... just make sure you have your usual PWO shake afterwards if you decide to do cardio after lifting.
When bulking, I don't think it is optimal to do cardio first thing in the morning.
Nor is it ideal to be doing too much cardio, although I do think it is beneficial to do some (2x a week), just to train the heart and for general health reasons. If you are doing slow cardio (i.e. 65 - 75% MHR), eat a protein/fat meal beforehand so your body will burn fat during the workout. If you are doing HIIT, you need carbs and protein beforehand because if you do HIIT properly, your body will be using glycogen as fuel, not fat. After HIIT, you need carbs and protein. After slow cardio, some people find it beneficial to eat another protein/fat meal to prolong lipolysis. Personally, I think it is just as beneficial to eat some complex carbs with protein. Then again, I've never really needed to go on a strict cutter before.
My 2 cents.