You might also try going to your service provider with the issue. Sometimes they have their own warranty/repair program. It is very, very unlikely that sweat would damage your phone, unless it was somehow pouring into the cracks between the shell of the phone. Telling us the exact problem, and what Samsung has allegedly done about it the past few times you took it in, would be helpful. As well as what they thought it was, and any other information you might be able to provide.

What exactly is the phone doing?

I purchased a Samsung Galaxy Ace in April 2012, since then I have had the phone in for service 3 times for the same problem with each time having three different opinions for the fault.
The last response from Samsung being to get a fourth opinion as the fault they believe in non warranty. they are now telling me the fault is water damage, something I find rather bemusing as I am 100% sure that the phone has not been exposed to water or moisture.

Could it be that my "sweat"" has damaged the phone!!!! or is this the easy way out for Samsung.

I am very disgruntled with the service I have received from this reputable Company.