The 34-year-old Garcia currently competes for the Corvette as a works driver in the TUDOR United SportsCar Championship.
He is a former test driver for China Racing, the NEXTEV TCR team's previous incarnation, and raced in the Punta del Este ePrix as a replacement for Ho-Pin Tung.
The NEXTEC team goes to the Russian capital with main driver Nelson Piquet Jr leading the championship standings, after Lucas di Grassi's exclusion from the race in Berlin last week.
Garcia is not the first reserve driver to be roped in for the Moscow ePrix, after Scott Speed was replaced by IndyCar's Justin Wilson racing for the Andretti team.
Speed is away on Global Rallycross duties.