Hello Mendoza,
Please refer to below link to see the explanation or definition of Sleep mode.
https://support.microsoft.com/en-us/windows/shut-down-sleep-or-hibernate-your-pc-2941d165-7d0a-a5e8-...When you device is in Sleep mode, it is not shut down.
In fact, A LOT OF things are still working in Sleep mode, so of course there will be battery drain.
So you may consider to check your battery setting, see if there is any program running in the background, screen brightness and so on.
Then let me know under what kind of setting or usage, how many % of battery drain during certain time period, when our technical support can better judge the issue.
Thank you.