I am somewhat chagrined to admit that I never realized those lines are measurements.
The most useful one—an 8 ounce line—was omitted, though.
If you’re at a picnic it might be acceptable to drink beer in a Solo cup, but if you’re at home, please, buy decent beer glasses. An exception being if you’re drinking Corona, Bud Light or similar ‘beer’, the Solo cups won’t hurt, so proceed.