It depends on the product. Anything not defined as “Hard Cider” as per 27 CFR § 24.331 is carbonated under 3.92g/l CO2. Actual “Hard Cider” has a limit of 6.4g/l but that is usually too much for foaming. You would be best to try out some carbonation levels on draft as see how far you can go before it foams.
Marcus is right. It depends on the product. If it is just Hard cider with no added ingredients you are allow to go as high as 6.4g/L, but that is normally way too high. At the company that I work for we carb everything to 1.95ATM (~3.8g/L) just to keep everything easy.