Not being a smartass,but it's really a simple 'one-step process' if you want to remain sober at this wedding; Don't drink. If that's too much currently...Do not go to the wedding and I'm sure the bride would understand and more than likely respect you more for,instead of you drinking because of her wedding.
If someone tried to "force me to drink" drunk or not.. that person and I would have a serious damn problem! Just sayin'.
Edit: Seriously..at a wedding EVERYONE is so caught up in the 'moment' and themselves no one will 'miss you' if you go and then leave early..no offense. However..drink and make an ass outta yourself..you'll be remembered. Trust me...I've been "that guy"!