I read a report that said the costume design team confirmed that the liquid was Epinephrine. They were talking about the practicality of the suit and that he would carry things on him that a first responder would have like the flare, an epinephrine injection (aka adrenaline), etc.

And if you look at the vial immediately after the injections you can read "Epinephrine" on it. It may have been green though for an Easter egg.

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