Phantom, too funny. When I was a young teen (ie at the age where everything about my parents embarrassed me) my mom took me to London for a theatre trip. (In hindsight this shows how ungrateful I was to still be embarrassed--my dad was working in Ireland for a year so we were going to spend a month with him, but my mom convinced dad to let me and her come a week earlier and see as many shows as possible in London--we saw 9 in a week, and they were all my choices). Anyway, we booked it to see Rent the first night there--like with no sleeps after landing. My mom did fall asleep at some point in Act I and kept up snoring so I'd wake her up and glare at her. She was fine after intermission though--I guess she just needed some winks (she now jokes about it because she also found the show way too loud, so the fact she fell asleep in that show...)
At the time, as a teen, I didn't even really believe that things like jet lag were real--now in my 30s I understand. Still, like everyone else here says, unless they are sleeping on you or snoring or whatever, who cares. If they're sleeping peacefully they're prob being a better audience member than half the audience there anyway (although for intimate shows I can understand why an actor might be put off by noticing a sleeping audience member).