I'd say he's around 5ft11 if you look at the match photos from our recent CL game -
https://mediacdn.mancity.com/-/medi...1920/dinamo-zagreb-v-city-11-dec/line-up.ashx
Jesus, Otamendi and Bravo are all standing on their tip toes (which I found amusing), but I'd say he's visibly a good 4 inches or so shorter than Rodri at 6ft3.
If Otamendi's feet are planted, I'd say he's ever so slightly taller than Garcia. Eric's still only 18/19 though, so there is still a bit of time for grow and wouldn't be surprised to see him hit the 6ft mark. Given the attributes to his game, I don't think this will be detriment to his career.