Maybe, but it’s probably not very effective. As there is no definitive chemical analysis of a homemade brew the usefulness will depend entirely on the person making the brew. I did not find any scientific studies of banana peel tea to reference so I researched the nutritional aspects of bananas and watched a few videos about homemade banana tea. None of which, I stress, had any basis in scientific research.

What I did find, and is common knowledge, is that bananas contain potassium along with a tiny bit of phosphorus and nitrogen, though much less. Potassium is important to a plant as it helps regulate the gas exchange process as well as water uptake and more. But a plant will need more than just banana peel tea to be nutritionally balanced.

Bananas are also high in sugar and carbohydrates which I find concerning. In the videos I watched they made their teas by filling a large jar with banana peels and water and letting them sit for several days then using the water for their plants. The water is cloudy by that time and quite possibly growing bacterial and fungal organisms. The small quantities of which are probably not going to harm a garden plant but I would NEVER put this on an indoor or potted plant. The sugars and carbs would be a feast for soil fungus gnats and other unsavory invaders which are remarkably annoying and very difficult to eliminate once established. If you do use it outside, I would suggest watering it in with plain water or at least diluting it quite a bit.

Other proponents suggested just burying banana peels in your garden. This is also problematic because decaying materials in the soil use some of the oxygen that your plant is seeking and attract organisms and insects which aid decomposition. Not really what you want to attract around healthy plants.

Yet another user suggested allowing the banana peels to dry in the sun until crispy and then powdering them and using them that way. Actually, the most obvious and best way to use those peels is in a good compost pile, managed properly and used when it is ready, but not everyone has the place for that.

As for your plants, the banana peel tea is probably okay and will do no harm to use outside. However, in my opinion, a well-balanced commercially available organic fertilizer would be a better bet.