I drink about 2 gallons of water a day and still experience an ammonia smelling body odor, Presser. It's not dehydration. It's caused from a process called "deamination." This occurs when the body breaks off the amino group from the amino acid and converts it to NH3 (ammonia). The ammonia is excreted through urine and perspiration.
Basically, you're burning protein for fuel instead of glucose, glycogen, etc. I experience this frequently. It doesn't necessarily mean that you're breaking down muscle tissue for fuel, just that you're catabolizing protein.