Those carbonated tablets are usually either sugar or light malt in tablet form to give beer a little extra sugar to ferment inside the bottle after the fermentation is just about done. This probably won't really taste good in mead so I'd just bottle it before the batch is completely done and let it carbonate itself on the honey sugar. It will be a little bit of a gamble until you get the hydrometer how much fermentation is left, you might want to put it into thick glass belgian style beer bottles just in case they carbonate a lot they won't break on you.

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