You could follow a solution similar to “How do I force “git pull” to overwrite local files?”:
git fetch --all
git reset --hard origin/abranch
git checkout abranch
That would involve only one fetch.
With Git 2.23+, git checkout is replaced here with git switch (presented here) (still experimental).
git switch -f $branch
(with -f being an alias for --discard-changes, as noted in Jan’s answer)
Proceed even if the index or the working tree differs from HEAD.
Both the index and working tree are restored to match the switching target.
If you do not want to switch branch, but only restore a folder from another branch, then git restore is the other command which replaces the old obsolete and confusing git checkout.
I presented git restore here.
git restore --source=anotherBranch --staged] [--worktree -- aFolder
# or, shorter:
git restore -s anotherBranch -SW -- aFolder