You can use line for that purpose. See this link
You can also use errorbar
V = [8 18 32];% Bar Value
x = [1.5 2.5 2];% errorbar x cord
y= [25 37 45];% errorbar y cord
e = [0.5 0.5 1];% errorbar error
p_val = {'p=0.037','p<0.0001','p<0.0001'};% strings
figure,bar(V,'LineWidth',1.5,'FaceColor',[0.7843 0.7843 0],'BarWidth',0.6)
ylim([0 50]),xlim([0.5 3.5]);
hold on,errorbar(x,y,e,'horizontal','LineWidth',2,'Color','k','LineStyle','none')
ax =gca;
text(x,y,p_val,'BackgroundColor',get(gca,"Color"),'HorizontalAlignment','center')
set(ax,'Linewidth',2,'FontSize',15,'FontWeight','bold','Ytick',0:10:40,'XTickLabel',{'A','B','C'})
