We had no problem doing this at BC Marketplace. We did it every day. We actually didn't know we could do it - the CM that was checking us out told us to go grab a snack since we have our mugs for our drinks.
The only park place we tried this at was Sunshine Seasons, and again we were told by the CM checking us out to go grab a dessert (cause we requested a cup for just water to drink with our meal).