Can stimulants like coke mask signs of intoxication?

I’ve been around someone who drinks heavily,15 to 20 drinks daily, often starting in the morning and continuing all day. It’s usually a steady pace, not a binge, but enough that they’re clearly dependent.

The other day, around midday, they were noticeably drunk (slurred speech, foggy). A couple hours later, despite continuing to drink, they seemed way more alert and coherent. It struck me as odd.

My gut tells me alcohol doesn’t just “wear off” mid-bender, so now I’m wondering, could they be using something else, like coke or another stimulant, to mask the effects?

Would appreciate any insight from people who’ve seen or experienced something similar.