Sippy cups are not at all a necessity, they are a fairly recent invention. They didn't exist when I and my siblings were growing up. Now they seem to be just an added source of frustration.
My daughter never wouldn't suck hard enough either, unless we took the valve out, so we just went with a regular cup at 14 months. All the kids at her daycare by 16 months were drinking out of regular cups (no covers even). We used the ones with the cover / spout sometimes, but no valve. She drank from a bottle at nap and bedtime, and a regular cup at mealtimes.
It's not unusual for her to want a bottle at night, either (I know some will argue that babies don't need to eat all night at some predetermined age, but I'm a believer that all babies are not the same, and don't run on a set schedule.) You are likely to be close to the end of the night feedings without taking any action.