Well there is so many choices, but I shall give you 2 answers!!!
If someone asks if you would like a drink you should simply say no thank you!!!
But there are some people who don't want to look weak or scared to their friends, so simply take it, when they shouldn't.
1. YOU can simply just walk away !!!!
or!!!!
2. You can simply say you don't feel like doing it now (LIE) to the person, who asks you !!!!!!
I would try and AVOID the situation, at ALL costs!
Hope this helps!!!