There is a machlokes between the mechaber and rma regarding the ratio of wine/water for something to be considered halachicly wine. There is a difference in how American and Israeli grape juice is made. israeli grape juice and certainly light grape juice is problematic according to the mechaber, while american grape juice, (and possibly even light) is not even for sefardim. I heard this in a shiur from a sefardi Rav, addressing making kiddush on grape juice.
Everyone should ask their own rav, their own shayla.