Hi Kelly,
Why are you yelling? You’ve certainly got my attention. Can we go to lowercase whispering and use your “inforum voice”? 
Different asana classes have different environments and therefore different needs. So we can only guess for you based on what you’ve shared.
If you have chosen a practice in which the external heat is increased then you might need water, a towel, and assorted other beach accessories.
If on the other hand you’ve selected a practice where that which is external is irrelevant, including the heat, then you can likely go to class without beachwear and get by on your normal daily hydration of half your body weight in ounce of consumed hydrating fluids.
A studio that has a sweaty practice should have a frisky mat cleaning protocol. That is something you should be shopping as the consumer. Please ask the studio “how often are mats cleaned?”. Otherwise, BYOM.
Yoga itself is experiential. And no two experiences are identical. Further, it would taint the process (for you) to try and tell you what you’ll get. That is why you are going, to find out what need/want/get. Enjoy that and soak up every drop - except the one plopping on the mat.