Invert sugar is "a sugar produced by chemical breakdown (by a process called hydrolysis) of sucrose (a type of sugar) into glucose and fructose." So it is actually a kind of sugar but is available commercially in liquid form, i.e. it is not liquified (مســال) , as liquification is a totally different chemical process. As for the term "invert" in this context, it refers to a chemical change or breakdown as we said earlier. We can't then say " مُحَـوَّر" as scientifically this would really mean modification or alteration in the nature of the substance, which is not the case. What I suggest here is to say:
ســكر سـائل محـوَّل
And I suggest that you add in footnote, explaining this type of change, or if it is not possible just put the content of the invert sugar between brackets, as in Arabic it needs some kind of explanation.