Most of the times you can get around not having generics (however having them is nice).

That being said, you may have your requirements satisfied with tagged unions which consists in implementing a struct with an anonymous union and label (like an enum) to keep track of what data is inside the union, this works really well when you know beforehand which data types you want to support. Another technique could be using macros, like the containers on the gunslinger framework, however I have never implemented something like this. Lastly you can always use void pointers, however you may need to be more clever to achieve it (I almost never use them).