This 24 hours restaurant is one of the best pho i found in downtown for late night. I mostly get beef pho and although not amazing, it is good enough for post-drinking food.
Their service is pretty decent considering how understaffed they are. Although servers are a bit too slow, but they are always nice
If you haven't tried yet, I would also recommend their spring rolls. These are not the typical skinny spring rolls you find in many restaurants. Instead, they are very thick and have lots of ingredients.
Like many places in Chinatown, this restaurant do not accept cards, so make sure you bring enough cash.