For some reason, congee and soy milk places are most popular for 4am food (there are always 24/7 places for those)
At least where I spent the most time a lot of the 4am crowd / food also the ‘European soccer’ fans time but instead of sports bars (it’s too early) it’s drinking tea and coffee and eating rice and noodles at ‘mamaks’. Like it was legitimately a ‘meet up with your friends at 4am at a specific place to watch English premier league or Spanish soccer and eat snacks together’ was a big part of my social life back home