You can get a 4/4 in the smallest cars (I have!).
Last gig I got my DB, two 10” cabs, two amps and a leads box. We also got two guitars, two guitar amps, a PA speaker on and a coat, all in a 2034 Dacia Sandero.
Fold down the seats and by turning the bass on its side, you can slide the neck between the two front seats and secure in place with a coat or some padding. Easy!