Passive is relative but here is my strategy through bitcoinaliens.
They offer hourly spins..? Giveaway things, its moderate but i often find myself doing several a day lol. Especially holidays or certain events as the payouts are more lucrative. They've they typical surveys, challenges and advertisement payouts but my bread and butter is the playtime feature. Earn 6 or 700,000 litoshi for playing x game... Sometimes combined with a challenge in said game when possible; along the line of reach castle lvl 17 in 30 days for 1.2 million litoshi or 1.2% of a litecoin. 
Surveys can pay pretty well for certain demographics but being a cis white male my opinion isn't typically what they're targeting. The degenerate in me did experiment and create my gf an account as they offer a really nice referral bonus with compounding earnings percentages that would make any pyramid scheme blush. Anywho, she qualified for far more lucrative surveys. Sample size maybe.. either way something to take note of.😈
Now on to what works for me
The caviout I've found is during x2 events. Download the new games to earn on then. You don't have to play or finish them that weekend, the rewards carry over for 30 days or you've earned your portion. Mostly all I do is leave said game on "playing" while charging during sleep, driving or work. They payout weekly if you've earned >100,000 litoshi and they cover transaction fees. Mine went straight to my blockfi to earn that succulent passive interest income. Rinse and repeat.
Typically I earn 1-3 million litoshi a month or 1.5-3% of a litecoin. As far as I can tell before blockfi lowered the rates* my degenerate android equals..ish the monthly interest earnings of about $1000 in ltc at 4.75% when not in use. Likely over earning those now that they've lowered the rates to 3.5% which prompted me to switch my payout address to nexo. Definitely moving my link 3.5% was painful to watch but 2.5🤮 while I dont hodl a lot there, my blockfi is shrinking fast.
My referal link if you're interested in letting your phone gather crypto crumbs
https://bitcoinaliens.com/?ref=3208823&game=8&pf=2
Idk why the link is not clickable, it did in my previous post & works if copy & pasted🤷
Heres where I'm going if you want in too.. https://nexo.io/ref/i6p7k5wb6z?src=android-link
Below is my aliens -> blockfi payouts over the past couple months along with my 9.11-9.23 ltc blockfi earnings. Not life changing but if crypto and litecoin grow and survive maybe even thrive it could be considered a legitimate secondary income.. sprinkle in a little inflation. What's 2% of 150 could be 2% of 10,000 one day.. never know, besides its free so💁♂️
