It's optional.
"If you looked through the window you’d think we were the perfect family but it’s tearing me apart. My friends say I should kick him out and only then will he realise what splitting up really means, because at the moment he’s having his cake and eating it."
More: I can't keep living a lie with my husband - Coleen Nolan problem page - Mirror Online
1- "Have your cake and eat it"
2- "Have cake and eat it too"
Does dropping the adverb too right here as Rover said "expecting listeners to finish them for themselves" or it is an optional?
It's optional.
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You could drop more than that and expect people to understand. It's such a well-known saying, you could probably get away with "He's having his cake ..."
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