Fossil told me they couldn't change my battery without paying for a whole new watchface, so here's my little teardown and change of a Fossil Gen 5 smartwatch.
*Please note that I did this without applying new adhesive, so it's no longer water resistant
Got a new battery from Aliexpress, works good so far: www.aliexpress.com/item/10050...
Please double check your watch battery is the same before buying any, mine was: APP00296
This specific watch model is a Fossil Gen 5 Carlyle Silver
It should work the same with Fossil Gen 5 / Fossil Julianna / HR FTW6035