I just started app stacking Actifit and Sweatcoin. Sweatcoin is easy to use, just like Actifit.
Here's my referral code if you decide to sign up.
https://sweatco.in/i/eliotpearson
The Sweatcoin store doesn't have as many great offers as Actifit. However, it's practically free coins because you use Actifit already.