Cinnamon has been shown to improve blood glucose levels and increase muscle insulin sensitivity but don't expect anything dramatic. It's kind of like how spicy foods will cause a slight increase in metabolism. It's 100% true but it's not like you are going to get shredded by adding hot sauce to your meals.
The same is true with cinnamon. It will cause a slight increase in insulin muscle sensitivity and help manage blood sugar but the effects will be minimal. If you enjoy the taste of cinnamon, add it to your meals. If not, don't stress.
The 2 best supplements for increasing muscle insulin sensitivity are:
1. fish oil
2. a good nutrient portioning supplement like n2slin
Don't waste your money on a cinnamon supplement. Your money would be much better spent buying #1 and #2 above ^^^