I drop one tablet into the toilet WATER TANK and one into the toilet bowl, let set for about 20-30 min and then use the toilet brush to clean up!

Also, I have used it to clear hair clogs in the sink but that didn't work as well, for some reason. 

I use it regularly to freshen my garbage disposal.

And to clean my jewelry.

Some good ideas here.  Change them up if you want to.

https://www.familyhandyman.com/list/uses-for-alka-seltzer-at-home/