It's not possible. A is a matrix of char, B is a matrix of doubles. All elements of a matrix must be of the same type.
What you can do is put them into a cell array, but the syntax for accessing elements is different:
C = [num2cell(A, 2) num2cell(B)]
%access elements of C:
cat = C{2, 1};
three = C{3, 2};
If A and B were of the same type and size (A=[4;5;6], B=[1;2;3]), you could just concatenate them
C = [A B];
