Pour out the required amount of beer in a bowl and let sit at room temperature 30-45 minutes.
Warm honey in the microwave for 25 seconds until thinned a bit. Add to the bowl with beer. Mix well until honey has dissolved. Add cider vinegar and Cajun seasoning and stir through. Let mixture stand for a few minutes.
Using a meat injector, carefully draw marinade into syringe and release excess air from it. Inject a small bit of marinade into multiple spots in the turkey. Cook bird as directed.
Remember to discard any remaining marinade that has come into contact with raw meat.
If making ahead of time, warm in the microwave for 15-25 seconds before using. The honey might re-thicken and this will prevent it from clogging up the needle.