How to heat frozen stuffed pretzels other than bake them
In case you do not have specific instructions from the company making them or a special warmer (see comments), I would try microwaving them first (e.g. defrost) and then broiling/baking them.

Alternatively, I've seen fast food cooks blast frozen foods in the microwave at high for a little while before throwing them into the deep-fryer, maybe that could be an option as well.

Or, since you mentioned that space/power/time is of the essence, you might even be able to use a combined microwaving/broiling function in case your oven offers it.

Experiment a little and you should be able to get the settings right quite fast.

PS: I'm assuming that thawing a few products beforehand is undesired and therefore leaving out that possible option.