I spent an hour or so looking for / trying coupons and nothing worked so I gave up and ordered from Amazon again.
I apparently waited too long on TRISHCOUNT and wasn't able to use it. I know it was $10 off the first shipment of a subscription, but was it one-time-use, or was anybody able to start a bunch of single-box subscriptions and get $10 off all of them?
FL0IB5S and FLH5E26 still appear to be accepted initially, but bomb out when trying to check out, AFTER you've entered your credit card info. They should just deactivate those completely and save people the trouble.
On the Amazon front, both Subscribe & Save and Prime Panty continue beating the pants off ordering directly from soylent.com, though if Amazon charges you sales tax, they difference may be fairly trivial. And of course this doesn't apply for powder, as powder is not available on Amazon except from shady resellers.
For Subscribe & Save, there's 20% discount on a single box that should still be valid, and that's on top of the normal 15% Subscribe & Save discount (for 5+ items shipping together), so really 35%, but only on a single box, one-time use.
I've also noticed that you can mess around with your Subscribe & Save date in order to get multiple shipments in a single month, although you still need to have 5 items per shipment to get the 15% discount.
Here's how Prime Pantry versus Subscribe & Save currently breaks down, not counting the aforementioned 20% thing. I use batches of 3 because that's what'll fit in one Prime Pantry box ($5.99 shipping), but this assumes that you'll be ordering enough to get 15% on Subscribe & Save
3 boxes of Cacao: $93.65 on Prime Pantry, $99.45 on Subscribe & Save: Pantry is $5.80 cheaper
3 boxes of Nectar: $110.84 on Prime Pantry, $99.45 on Subscribe & Save; Subscribe & Save is $11.39 cheaper
3 boxes of 2.0: $107.99 on Prime Pantry, $86.70 on Subscribe & Save; Subscribe & Save is $21.29 cheaper
3 boxes of Coffiest: $122.50 on Prime Pantry, $99.45 on Subscribe and Save; Subscribe & Save is $23.05 cheaper
Panty prices seem to vary a lot so it's probably worth checking often
Cocao on Pantry is pretty cheaper right now, cheaper than 2.0 on Pantry, but not as cheap as 2.0 on Subscribe & Save.
There's some deal on Pantry to get free shipping if you order 5 non-Soylent items from a certain list of eligible items. I looked at it and it seems to all be name-brand stuff so probably not a great deal but if you need other stuff maybe you can make it work for you.
With Prime Pantry, you can fit 3 Soylent boxes in each Prime Pantry box with some room left over. Shipment on each Prime Pantry box is $5.99. Coffiest is apparently very slightly smaller; it's still 3 per Prime Pantry box, but they claim to be able to fit 10 Coffiest boxes in 3 Prime Pantry boxes (with 0.2% space left over), so if you can handle that much at once, that might be an option. For anything other than Coffiest, it says you can do 13 Soylent boxes in 4 Prime Pantry boxes.
I had some numbers in this post wrong but I think I've edited everything accordingly after double-checking.