Worth noting that Coffiest (Soylent's latest drink product) contains both caffeine and L-theanine. Their ratio is questionable (150mg caffeine, 75mg L-theanine), but subjectively I have found it to be a great way to boost my productivity in the morning, and I've never noticed jitters or anxiety despite the (relatively) high dose of caffeine. I also prefer the taste to regular Soylent -- no "wet cereal" aftertaste, and you can add a bit of sugar or chocolate syrup if it's too bitter for you.