Franzia is (IMO) crap. I wouldn't make sangria with it. We buy a lot of box wine because it is extremely convenient for camping trips and when you want a glass or two. Opening an actual bottle of wine is an "occasion" type thing for us.
Bota makes what we think is hands down the best red in a box: "Redvolution." It is their own proprietary blend and it beats the heck out of the other boxed reds we have tried. Otherwise, reds from Bota, Black Box and Fish Eye are usually reliable. If you like Australian shiraz, Banrock Station offers a nice one in the box.
Whites are usually reliable from Bota, Black Box and Fish Eye, but some have more varietal character than others. Chardonnay in general makes me go a big, floppy wobbler, but Black Box and Bota's are decent. We like the Moscato from Fish Eye and the Riesling from Bota. Black Box used to have a Snake River riesling that was really good, but it may have been a one time deal since I have not seen it in a while.
When you buy box wines, look carefully at sell by dates. Unlike bottled wines, box wines do not keep forever and I pay close attention to freshness when I buy. Older stuff tends to lose distinct flavors and sometimes tastes oxidized.