You could create a 3D plot, and then rotate it so you are just looking at the XY plane. You can do this using view(2). You could try to use color to represent the value of your 3rd variable.
What works is going to be very dependent on your data. You might consider the answer provided here if your plot is a line.
% 3D
t = linspace(0,10,500);
xt = exp(-t./10).*sin(5*t);
yt = exp(-t./10).*cos(5*t);
patch([xt NaN],[yt NaN],[t NaN],[t NaN],'FaceColor','none','EdgeColor','interp');
xlabel("X")
ylabel("Y")
zlabel("Time")
cb=colorbar;
cb.Title.String = "Time";
colormap jet
view(3)
%2D
figure
patch([xt NaN],[yt NaN],[t NaN],'FaceColor','none','EdgeColor','interp');
xlabel("X")
ylabel("Y")
cb=colorbar;
cb.Title.String = "Time";
colormap jet
