There are a few ways to do this. The best option in any situation depends on how your data are organized (or can be organized) and the amount of fiddling necessary to get the desired bar colours, tick labels, etc.
This first solution plots two sets of data, one stacked and the other with single bars. The bar widths and positions are adjusted as per your needs. There is a tick label for each group of unstacked+stacked bars.
n = 5;
x1 = rand(2,n)
x2 = 2 * rand(1,n);
b1 = bar(x1','stacked');
hold on;
b1(1).BarWidth = .4;
b1(1).XData = (1:n) + .25; % move stacked bars right
b1(2).XData = (1:n) + .25;
b2 = bar(x2);
b2.BarWidth = 0.4;
b2.XData = (1:n) - .25; % move single bars left
The second solution expands the two sets of data to include 0s either in the odd positions for the stacked bars or in the even positions for the single bars. Each bar has an x-axis tick and tick label.
n = 10;
odd = ~rem(1:n,2);
even = rem(1:n,2)
x1 = rand(2,n) .* odd;
x2 = 2 * rand(1,n) .* even;
b1 = bar(x1','stacked');
hold on;
b2 = bar(x2);
The third solution uses a single set of data but nulls out the odd entries in one column. All the bars are stacked but half the values in one set are zero.
n = 10;
odd = logical(rem(1:n,2));
x = rand(2,n)';
x(odd,1) = 0; % make every second value 0 in 1st column
bar(x,'stacked');
