How do I print various datatypes in void function in C++

As Richard had already pointed out, a data type is needed that fits all passed parameters. As usual you can define such a type yourself, if nothing fits in the standard. My suggestion here would be a class multitype, which provides an overload for all needed parameter data types and can also restore these data types as ostream. The call would then look as desired:

void printValues(multitype val1, multitype val2)
{
	cout << val1 << " " << val2 << endl;
}

int main()
{
	printValues(10, 20);
	printValues(30, "Hello");
	printValues(2.5, 7.5);
	return 0;
}

Since the multitype data type does not yet exist, it must first be defined. This could look like this, for example:

class multitype {
public:
	multitype(int d);
	multitype(double d);
	multitype(std::string mts) :_s(mts) { _typ = T_STRING; };
	multitype(const char* mts):_s(mts) { _typ = T_STRING; };
	enum DDTYPE { T_NONE, T_INT, T_DOUBLE, T_STRING };
	DDTYPE getype() { return _typ; };
	std::string getdata_s() { return _s; };
	friend ostream& operator<<(ostream&, multitype&);
private:
	DDTYPE _typ;
	int  _d;
	double _dd;
	string  _s;
};

The rest is housework and I like to leave that to the questioner. I still briefly give some outlines here:

multitype::multitype(int d) { /* TODO */  };
multitype::multitype(double d) { /* TODO */ };
ostream& operator<<(ostream& os, multitype& mt) { /* TODO */ return os; };