it really depends on whether your it's in total $100s or $1000s. $100s i would just list as "other income" on schedule 1 line 8. $1000s I would list amounts for each major category with a description then group the smaller amounts as "other income"
Plasma donations will definitely be in the thousands since I'm making about $400 /month.
Surveys will probably peak at $1000-1200 total for the rest of the year. Those are like 90% from one source.
I heard that rebates aren't taxable. Would rebates include things like deposit $50 get $100 back? or buy subscription for $10 get $20 back? That will probably peak around $1000-1200 like the donations. Good short term money but not sustainable since every website has the same offers. Some of the things I've gotten money for doing (like playing a game) aren't something I had to put in money for though so those would surely be taxable?
I think by the end of the year my extra income from all these sources would probably be $3000-4000
Rebates are not taxable since it is just your own money coming back to you.
The blood and surveys are taxable and can be entered on the Sch 1 line 8 as income not subject to SE taxes however be prepared to defend this choice if the IRS sends you a notice. You should get a 1099-misc for these incomes which will make things easier to defend.