Update:
myString = "abcdefg";
myChar = char(myString);
% using array indexing
myNewStr = string(myChar(end:-1:1));
% using FOR loop:
myNewChar = [];
for i = 1:length(myChar)
myNewChar = [myNewChar,myChar(end-i+1)];
end
myNewStr = string(myNewChar);
% myNewStr =
% "gfedcba"