How to express "same shit, different names" in Mandarin?
Two set phrases come up to my mind:


炒冷饭 (heat leftover meal/rice)
新瓶装旧酒 (the same wine in a different bottle). 旧药换新瓶 is a less common variation.


They're both applicable to your context. Their literal meaning is almost never used.

Example:


  大多数电子游戏的续作都是新瓶装旧酒。A lot of video game sequels are just rehash of the previous installation.