Vietnamese people are early birds. Vietnamese people are badminton cracks. You should know this before!
So if you're interested in watching sports get up early and visit Ho Hoan Kiem or Lenin Park. It is not uncommon to see people playing badminton as fast as tennis pros early in the morning! The same is true for all those who prefer a less exhausting sport: Tai Chi. In the morning and the evening, the shores of Ho Hoan Kiem are full of mostly elderly people working out. One is surprised how fit they are: Lithe and lissom without any signs of being exhausted!
Btw, on the right side of Ho Hoan Kiem, in the little park near the post office, you can sometimes come across a woman who seems to train a whole group. She's got a radio with crappy music and the whole group does the same moves which she tells them. Looks like aerobics a la Vietnam!
If you come early in the morning to the banks of the Hoan Kiem Lake you will witness some scenes of locals (mainly old people) practicing this oriental exercise-philosophy. They make a nice relaxing scene, with their sloooooow movements and balanced positions...
I tried to follow them (I did 2 years of Taichi back at home), but the movements were different from the ones I knew, and I made a pathetic figure trying to follow up all the movements, so I withdrew and went for a morning coffee with a croissant!
Try out Tai Chi at Hoan Kiem Lake at around 5:00 AM. It'S an experience! If you are not awake at that time join the gym at the Hanoi Sofitel. They also offer Tai Chi at around 7:30 AM.
Equipment: wide shirts and trousers, no shoes