I can't delete apps from my i watch in order to get required space to update my watch.

Unpair and update your Apple Watch

1. Keep your Apple Watch and iPhone close together as you unpair them.
2. Open the Watch app on your iPhone.
3. Go to the My Watch tab and tap your watch at the top of the screen. 
4. Tap the info button  next to the watch that you want to unpair. 
5. Tap Unpair Apple Watch.
6. For GPS + Cellular models, choose to keep your cellular plan. 
7. Tap again to confirm. You might need to enter your Apple ID password to disable Activation Lock. Before erasing all content and settings on your Apple Watch, your iPhone creates a new backup of your Apple Watch. You can use the backup to restore a new Apple Watch.

Next, set up your Apple Watch with your iPhone. When asked whether you want to set up as new or restore from a backup, choose to set up as new. Then follow the onscreen instructions to finish setup. If you want to update to the watchOS beta, reinstall the beta profile after setup is complete.

Finally, update your Apple Watch.

For more information, see here: https://support.apple.com/en-us/HT211283#unpair

Press the Digital Crown on your Apple Watch to bring up the App View.

If you're using List View, swipe left across the app you want to remove, then tap the red trash button. If you're using Grid View, tap and hold to activate jiggle mode, then tap the X in the top-left corner of the app you want to remove.

Tap Delete App to confirm.

Not all apps are available to delete.