Carbs drive up insulin which is the shuttle hormone that puts nutrients into your cells. So, you need carbs, insulin, food, and water, to maintain the pump, along with ongoing exercise.
The really huge guys you see use over the counter or prescription insulin to stay "carbed up" / "full". Exogenous insulin drives the fluid into the muscle not only helping to promote growth but also putting more glycogen in the muscles so that you have higher performance later.
Insulin is also the most anabolic hormone there is, and that's why guys are so much bigger these days than in yesteryear. The science is MUCH better compared to how it once was.
Any use of insulin should be done in a guarded and educated fashion. Like anything from aspirin to food, used improperly, it can be lethal. Of course, type 1 diabetics use insulin all day long, every day, without much incident. so it's important to be rational in your thinking. Cars will kill you, too. :-)
For most folks, carbs, protein, and water, along with regular exercise is the right path, but, you asked the question and I gave you the answer. Fast carbs, that is SUGARS, immediately post workout during the golden hour post workout will carb you up like crazy and you don't need to worry about getting fat. About 30 to 40 grams of sugar post workout, along with 30 to 70 grams of starch, and about 40 grams of protein, post workout, will carb you right up, and shuttle nutrients into your muscles and promote better gains and performance.