Who doesn't love a summer sangria? From time to time, people will ask which wines make the best sangrias and whether or not the wine really matters in the whole mix? The wine does make an impact on the final pitcher of sangria, in much the same way that the choice of wine used in cooking influences a dish - so try to pick a wine that you would enjoy drinking regardless of whether it were to end up in a sangria recipe or not. That said, it might be prudent to keep the wines around the $10 mark, since you won't be focusing in on the wine's intrinsic qualities and subtle nuances, but going more for the big picture flavor profile.
One of the beauties of Sangria recipes is that you can use a variety of different wines in the recipe mix. It's often wines that have not been finished the day before that find their way into a Sangria recipe, or wines in the "good value" category that make for a perfect Sangria blend. All of the wines listed in the "Sangria Wine Guide" are good wines on their own, that have been selected for their specific flavor profiles and style components that tend to highlight the various fruit additions in the specific Sangria recipes.
Check out the Best Wines for Making Sangria Guide.