Having a bitcoin rewards card like fold offers is probably the most efficient way.

If you are looking for "free sats" that don't require any purchase attached, the most success I have had is with Fountain podcasting app. I have stacked around 85k sats listening to podcasts on the app since last July when I joined. They seem to give out less sats now then they did back then but still pretty good, can usually stack a couple hundred a day.

I second fountain. It’s very reliable in that I get at least 140/day, often more. Many of the games in the space feature a chance to earn Bitcoin, nothing guaranteed.

I like zebedee and Thndr games but I don't play enough to earn a lot of sats. I am happy if I can stack a couple hundred a week between the two.

BM app is pretty good too especially when they do the boosted articles like they have right now. You can stack around 500 sats a week if you catch their weekly 200 sat code along with stacking for reading articles.