How to keep concentration during games?

Hi All, I have a question regarding concentration

To cut a long story short, I play badminton a lot (12-16 hrs a week) and have been described as “advanced”. But can struggle with concentration and decision making during ralleys. Or I could be described as lazy and don’t push myself to be that bit faster, that bit more aggressive etc.

Last night though, had a great evening at my social plastic club. Won almost every game and was playing at 95% of my potential it felt like. What caused this change? I had a Monster Energy drink about 6 hrs before playing.

I don’t drink tea or coffee, hate the taste. And I donated a kidney this year so I have to be very careful about dietary things and substances (35 yr old male).

I don’t want to rely on this for an increase in performance. Are there any safer things I can consume or things I can do to get the same effect? (UK).