Hot glue wooden sticks to the back of the mini liquor bottles. Don't worry if the bottles are plastic, they shouldn't melt.
Cheers to 21 years alcohol basket for him instead of making him a cake. unless he likes cake then make him a cake to
35 Easy DIY Gift Ideas Everyone Will Love- personalized beer glass with a few minis would be a great birthday gift! (put great year instead of 21 years)