I started falling asleep over and over again at dinner too in front of my parents when I had a particularly large prescription of hydromorphone.
I don't even remember my excuse but it's kind of sad how willing parents are to accept the lamest excuses when they don't expect their kid is taking drugs. One particularly fucked up Christmas, I locked myself in the bathroom doing an 8-ball of coke for 8 hours, missing dinner. I said I was just sick. I had a beard at the time but all the coke had me paranoid that the powder had gotten into my beard and I couldn't get it out, so I ended up completely shaving before leaving the washroom that night, with the excuse that I had puke in my beard that I wasn't able to wash out...