"I want a sandwich too!"
Translation:Ik wil ook een boterham!
No, in this sentence ook has to come after the verb in order for it to be correct Dutch. Usually ook comes after the verb (if there is one) or right after the subject pronoun, for example "Ik ook!" (Me too!) There are a few idiomatic expressions where "ook" comes at the end, for example: "Dat is waar ook!" (That's true, of course!), but in this case it doesn't mean also or too.