One attendee, Dan Carroll, founder of the education tech start-up Clever, complimented Mr. Mittal for mixing peanut butter into the oatmeal-colored drink to accompany the pad thai. “That was very thoughtful, that you really tailored the Soylent experience to the food,” Mr. Carroll said.

The rise of the meal replacements mirrors Silicon Valley’s start-up froth — and includes a dose of confidence. The makers of the new drinks said their products were better than the commercial powders that had been on the market for years, because those tended to have lots of sugar and overemphasized the use of protein. In contrast, Soylent and Schmoylent are both blends of nutrients that would allow one to drink only those meals and live a healthy life, they said.

Rob Rhinehart, a software engineer, said he came up with the idea for Soylent in 2013 while working long hours at a wireless communications company and realizing he was eating poorly. He said he wanted to create something that could be “universally applicable” for hard-working people like himself. So he founded Soylent, based in Los Angeles, that year and gained more than $3 million in funding from the crowdsourcing site Tilt.

Orders took off quickly. The company said it had shipped more than the equivalent of six million “meals” across the United States. Mr. Rhinehart declined to share financial details but said his company was shipping “at the kiloton scale” each quarter and had attracted $24.5 million in financing. While Soylent has a diverse customer base, tech workers in particular have the “early-adopter personality” that makes them open to trying the powder, Mr. Rhinehart said.