Below are a few such streaming services.

1
Stream the ATP Finals on DirecTV Stream. DirecTV Stream is typically our top recommendation for anyone looking to watch sports (including tennis) without cable. ...
2
Stream the ATP Finals on Sling. ...
3
Stream the ATP Finals on fuboTV.
Area
ATP Masters 1000s
ATP 250s
Turkey
S Sport
S Sport
Ukraine
Setanta
N/A
United Kingdom
Sky UK
Sky UK
United States*
Tennis Channel
Tennis Channel