What version of bat are you using?
0.15.4

Describe the bug you encountered:
Using export MANPAGER="sh -c 'col -bx | bat -l man -p'"
results in -bx: 1: Syntax error: Unterminated quoted string

Describe what you expected to happen?
paging with bat

How did you install bat?
Void Linux package manager

** The bug **
It was already reported here for Termux, and it coudl well be the case for Alpine and other Mandoc's man implementations cases.
See termux/termux-packages#4781 (comment)

** Lazy solution **
Instead of recompiling man from GNU (https://www.nongnu.org/man-db/development.html)
one can be using export MANPAGER='nvim +Man!'