I use Bonine and our family has for years. I need it mostly for spinny rides and it seems to help, somewhat. It's not 100% great every time, but it does the trick.
Since it's good for 24 hours, I usually take it right before I go to bed so that if it makes me sleepy, it's ok. Also, I make sure I ride the rides I think will make me sick first thing, so if it starts to wear off in the afternoon/evening, that's ok.