how to open trunk of a 1989 560sl without battery being hucked up

You can hook up a small or big charger to the battery cables long enough to pop open the trunk. Or you can jumper to another car or lawn mower. But be very careful about polarity. In the event you can not reach the battery cables due to a locked hood, you can plug a trickle charger into the cigarette lighter. Might turn on the key to activate that. I hope this helps.