In a pinch when out of tartar sauce I’ve mixed green relish with mayo and it’s, passable.
For that matter, mayo with hot sauce and ketchup was my accompaniment to some otherwise bland pizza and tater tots this afternoon.
Microwave Hollandaise sauce. Can go wrong easily, but when I wanted it quick it works fairly well. Just have to tend the microwave every 15-20 seconds to mix it before it coagulates. But it’s done its job more than once for me.


Sauces for what? A lot of sauces you can buy pre-made and are perfectly acceptable—also some sauces you would not normally make yourself, e.g. soy sauce.
Sauces as in dipping sauces, I normally use pre-made hot sauce.
You can also make a lot of passable pasta sauces very easily. One way is to fry up garlic, chilli, and any other aromatics you like in a pan. Add white wine. Add parsley. Add pasta water. Add spaghetti (or other pasta).
Another pasta sauce I like that’s very easy to make is just putting silken tofu and miso paste into a blender/food processor and blending until creamy smooth. There should not be any chunks; it should be completely smooth and creamy. If you see any lumps at all, keep blending—it will get smooth. That makes for a good creamy vegan sauce you can put on pasta or other things.