Does all sweat smell or just nervous perspiration?
That characterictic odor is not the sweat itself, but the result of bacteria decomposing it. Put a glass of sweat into a refrigerator, and it won’t smell.
As to why “nervous perspiration” seems to smell worst is either because:
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Your own imagination
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Since you’re nervous, you tend to have hightened senses which make small smells smell big.
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“nervous perspiration” contains more stress chemicals that was release by your body as a reaction to stress. These chemicals may make the bacteria decomposing it work a whole lot more and hence the greater smell.
This is just my guess and i’m no expert…so lets wait for people to come correct me.
As someone said, “Don’t sweat petty things and don’t pet sweaty things” 
Cecil did a column on Chinese people’s sweat in the last two weeks, dealing with smelly sweat glands and non-smelly sweat glands. I don’t feel like wrestling with search engines right now, but maybe you do. My ISP hasn’t treated me kindly in the last few days, and I don’t feel like getting brick-wall marks on my forehead.
–Nott
Asian sweat: http://www.straightdope.com/columns/021004.html
My own theory is that the small amount of liquid down in your pores builds up bacterial decay-stink, and if you suddenly start sweating, it pushes the stinky slime out of the ducts so it can suddenly start evaporating. So, when we first start exercizing does our sweat also smell briefly worse?
This guy below is on to something:
Project Kill B.O. http://killbo.com/
I tried it and I killed my underarm odor. It was like being a little kid again. The secret is to first wash all of your shirts with chlorine bleach (1/3 cup per load), then scrub underarms well and use bacteriacidal deodorant (such as Mitchum, etc.) It doesn’t matter how hard you scrub yourself or what chemicals you use, if your shirts are not sterilized they will reinfect your underarms within hours.
I find that one “KILLBO.ORG” treatment lasts about ten days. I can actually go without bathing for ten days, and all the stench comes from (ahem) elsewhere, while my underarms have almost no smell at all. In the past I had to shower and scrub well every single day or by the end of the day I would stink out the guys in neighboring cubes.
Interesting that the bacteria in shirts normally survives both laundering and the heat of the dryer. Perhaps it’s an evolutionary effect, where bacteria types which can’t hide out in clothing will tend to be eliminated. Another benefit of adding bleach to laundry: if you accidentally forget to stick a wet load in the dryer, and you leave it all week, it has no scent and you won’t have to re-wash the load. That “rotting washcloth odor” is clearly bacterial.