Les Gones were beaten 2-0 by the Spanish outfit at the Stade de Gerland last week and face an uphill task of overturning the two away-goal deficit.
While he is unsure of how Sociedad will line up, Garde knows that Lyon will need to be far better in the return leg.
"We came up against a really good team in the first leg, but I don't really know what Real will do [on Wednesday]," Garde told reporters. "What I do know is that my team will have to play much better and I know we are capable of doing that.
"We were battered and bruised at home and I think that my team are better, individually and collectively, than what they produced in that game. I don't need to convince them of that.
"The defeat against Reims was also unfortunate, but we need to separate the two competitions. We have proved since the beginning of the season that we have a quality squad, capable of winning away from home."
The match kicks off at 7.45pm.