Yes I use Sleep Watch. It used to only use around 5-8% at most on S3 running OS 4
I starting to wonder if these are not optimized for watchOS 5. I had sleepmatic and autosleep. On watchOS 5 I started seeing a drain of 20%. I deleted sleepmatic as it’s not a large developer and kept autosleep. I think it’s running fine as I saw about 7% drain last night. Might want to try another sleep tracking app.