I'm 14 years old and I was at a volleyball training yesterday and we did a lot of fitness and body workouts and we were dehydrated and I started to see black and green noise in my vision and it spread more by time and I felt heavy and my ears began to not hear properly with a whistle kind of noise and I felt like vomiting and fainting but it was gone after 2-5 minutes, I feel like it is a mini-stroke but I wanted a clear answer from an expert, also my identical twin experienced that too at the same time. Note: it happened to me before too from 2 years in my karate training.