I grow sweet peas, both in the ground and in very large pots. The scent is Devine.
My pot grown ones are in the courtyard and as others have said require very large pots,45/50 cms, humus rich compost and kept well fed and watered. As they also need very regular watering, I put a large plant pot with good drainage holes, in the middle, fill the compost around it and then plant up in the usual way around the edge.
Then I fill the middle pot with water, it acts as a water reservoir and as long as it’s filled the plants don’t dry out. Once a sweet pea has been deprived of water, then it can’t be revived and dies. I feed mine with tomato feed, again through the reservoir.