laboriously
He read through the drudgingly long list of work that needed to be done.
We drudgingly made our way across the muddy field.
He wrote slowly and drudgingly through the night.
They followed him drudgingly, showing little or no enthusiasm.

SMART Vocabulary: related words and phrases

Effort and expending energy
assiduity
assiduous
assiduously
assiduousness
be running on emptyidiom
burn
effortful
effortfully
elbow grease
fight
hamster wheel
hard at itidiom
kill
plough
plough through something
push
put something in/put something into something
rearguard action
set/put your mind to somethingidiom
swing