It really varies with the particular type of car. Some are rather easy to pop the hood on from outside, some are nigh unto impossible. But it’s not the kind of thing anyone would know offhand, unless they just happen to remember doing it on that particular model, and it’s not covered in repair manuals. I wouldn’t be able to tell how to do it, or how easy/hard it is, without looking at the car in question.
On many cars it’s possible to access a wire that connects to battery positive from underneath, as mentioned above. This would usually be a starter cable, though there are other possibilities. It would involve jacking up the front end and connecting a jumper wire (not jumper cable - they’re too big) with an alligator clip on it. Again, I wouldn’t know the feasibility of this without looking at the car (although I could probably make a good guess for some cars, if my repair manuals give enough info to determine the starter location).
If you don’t have someone available who has a good sense of how either of these might be done, you’d probably be time and money ahead to call a locksmith.