How big could you get a plant in a 50 gallon drum?

If you grew 1 plant out of a 50 gallon drum how big could the plant grow? seeing as it has unlimited space to grow roots

Many factors will come into it like available light and veg time and medium. I flower my coco trees in 16 gallon grow bags and getting everything right up until they are ready too flower isn't always easy. Seems the quicker I can get them too veg the more they yield in the end with better health.

Fast veg is the key

Try it is all i can say