In my home we observe this rule very strictly.
The five kind of food items that are prohibited to eat during night times are
Nellikai or Amla
Oorukai or Pickle
Inji or Ginger
Keerai or leafy vegetables
Thayir or Curd
There may be a reason why these foods are prohibited but these restrictions also depends on the climatic conditions we live.
Curd gives heat to our body and thus before sleeping during night times ,curd is prohibited.
I have heard many people who have told they have sinus problems take curd during night time and doctors also tell people not to eat curd during night.
During night times, our body produces more heat and after we wake up, when we take bath ,this heat is released and if we take curd during night times, our body produces more heat.
In north India, consuming curd is common during night times as winters are long in north but in South ,curd is taken only during morning and especially during afternoons of winters and if its summer we go with butter milk.
Moreover, even while serving Ilai sappadu( plaintain leaf meal), curd is served last during winters while Mor( butter milk) is replaced instead of curd during summers.
In winter, our body needs heat whole during summer, we need to cool our body.
Thus curd is bad during summers and during night times instead you can go with butter milk during summers.
Similarly the other 4 mentioned foods will be having a reason they we should find.
Whatever our ancestors have told, its for a reason!